Then a + b = b + a, a+(b + c) = (a + b) + c.
Adding zero does not change the number, but the sum of opposite numbers is zero.
This means that for any rational number we have: a + 0 = a, a + (- a) = 0.
Multiplication of rational numbers also has commutative and associative properties. In other words, if a, b and c are any rational numbers, then ab - ba, a(bc) - (ab)c.
Multiplication by 1 does not change a rational number, but the product of a number and its inverse is equal to 1.
This means that for any rational number a we have:
a) x + 8 - x - 22; c) a-m + 7-8+m;
b) -x-a + 12+a -12; d) 6.1 -k + 2.8 + p - 8.8 + k - p.
1190. Having chosen a convenient calculation procedure, find the value of the expression:
1191. Formulate in words the commutative property of multiplication ab = ba and check it when:
1192. Formulate in words the associative property of multiplication a(bc)=(ab)c and check it when:
1193. Choosing a convenient calculation order, find the value of the expression:
1194. What number will you get (positive or negative) if you multiply:
a) one negative number and two positive numbers;
b) two negative and one positive number;
c) 7 negative and several positive numbers;
d) 20 negative and several positive? Draw a conclusion.
1195. Determine the sign of the product:
a) - 2 (- 3) (- 9) (-1.3) 14 (- 2.7) (- 2.9);
b) 4 (-11) (-12) (-13) (-15) (-17) 80 90.
a) B gym Vitya, Kolya, Petya, Seryozha and Maxim gathered (Fig. 91, a). It turned out that each of the boys knew only two others. Who knows whom? (The edge of the graph means “we know each other.”)
b) Brothers and sisters of one family are walking in the yard. Which of these children are boys and which are girls (Fig. 91, b)? (The dotted edges of the graph mean “I am a sister,” and the solid ones mean “I am a brother.”)
1205. Calculate:
1206. Compare:
a) 2 3 and 3 2; b) (-2) 3 and (-3) 2; c) 1 3 and 1 2; d) (-1) 3 and (-1) 2.
1207. Round 5.2853 to thousandths; before hundredths; up to tenths; up to units.
1208. Solve the problem:
1) A motorcyclist catches up with a cyclist. Now there are 23.4 km between them. The speed of a motorcyclist is 3.6 times the speed of a cyclist. Find the speeds of the cyclist and the motorcyclist if it is known that the motorcyclist will catch up with the cyclist in an hour.
2) A car is catching up with a bus. Now there are 18 km between them. The speed of the bus is the same as that of a passenger car. Find the speeds of the bus and the car if it is known that the car will catch up with the bus in an hour.
1209. Find the meaning of the expression:
1) (0,7245:0,23 - 2,45) 0,18 + 0,07 4;
2) (0,8925:0,17 - 4,65) 0,17+0,098;
3) (-2,8 + 3,7 -4,8) 1,5:0,9;
4) (5,7-6,6-1,9) 2,1:(-0,49).
Check your calculations with micro calculator.
1210. Having chosen a convenient calculation order, find the value of the expression: 
1211. Simplify the expression:
1212. Find the meaning of the expression:
1213. Follow these steps:
1214. The students were given the task of collecting 2.5 tons of scrap metal. They collected 3.2 tons of scrap metal. By what percentage did the students complete the task and by what percentage did they exceed the task?
1215. The car traveled 240 km. Of these, 180 km she walked along a country road, and the rest of the way along the highway. Gasoline consumption for every 10 km of a country road was 1.6 liters, and on the highway - 25% less. How many liters of gasoline were consumed on average for every 10 km of travel?
1216. Leaving the village, the cyclist noticed a pedestrian on the bridge walking in the same direction and caught up with him 12 minutes later. Find the speed of a pedestrian if the speed of a cyclist is 15 km/h and the distance from the village to the bridge is 1 km 800 m?
1217. Follow these steps:
a) - 4.8 3.7 - 2.9 8.7 - 2.6 5.3 + 6.2 1.9;
b) -14.31:5.3 - 27.81:2.7 + 2.565:3.42+4.1 0.8;
c) 3.5 0.23 - 3.5 (- 0.64) + 0.87 (- 2.5).
People, as you know, became acquainted with rational numbers gradually. At first, when counting objects, natural numbers arose. At first there were few of them. Thus, until recently, the natives of the islands in the Torres Strait (separating New Guinea from Australia) had in their language the names of only two numbers: “urapun” (one) and “okaz” (two). The islanders counted like this: “Okaza-urapun” (three), “Okaza-Okaza” (four), etc. The natives called all numbers, starting from seven, with a word meaning “many.”
Scientists believe that the word for hundreds appeared more than 7,000 years ago, for thousands - 6,000 years ago, and 5,000 years ago in Ancient Egypt and in Ancient Babylon names appear for huge numbers - up to a million. But for a long time the natural series of numbers was considered finite: people thought that there was a largest number.
The greatest ancient Greek mathematician and physicist Archimedes (287-212 BC) came up with a way to describe huge numbers. The largest number that Archimedes could name was so large that for him digital recording a ribbon two thousand times longer than the distance from the Earth to the Sun would be needed.
But they had not yet been able to write down such huge numbers. This became possible only after Indian mathematicians in the 6th century. The number zero was invented and began to denote the absence of units in the decimal places of a number.
When dividing the spoils and later when measuring values, and in other similar cases, people encountered the need to introduce “broken numbers” - common fractions. Operations on fractions back in the Middle Ages were considered the most complex area mathematics. To this day, the Germans say about a person who finds himself in a difficult situation that he “fell into fractions.”
To make it easier to work with fractions, decimals were invented fractions. In Europe they were introduced in X585 by the Dutch mathematician and engineer Simon Stevin.
Negative numbers appeared later than fractions. For a long time such numbers were considered “non-existent”, “false” primarily due to the fact that the accepted interpretation for positive and negative numbers“property - debt” led to confusion: you can add or subtract “property” or “debts,” but how to understand the product or quotient of “property” and “debt”?
However, despite such doubts and perplexities, rules for multiplying and dividing positive and negative numbers were proposed in the 3rd century. the Greek mathematician Diophantus (in the form: “What is subtracted, multiplied by what is added, gives the subtrahend; what is subtracted by the subtrahend gives what is added,” etc.), and later the Indian mathematician Bhaskar (XII century) expressed the same rules in the concepts of “property”, “debt” (“The product of two property or two debts is property; the product of property and debt is debt.” The same rule applies to division).
It was found that the properties of operations on negative numbers are the same as those on positive numbers (for example, addition and multiplication have the commutative property). And finally, since the beginning of the last century, negative numbers have become equal to positive numbers.
Later, new numbers appeared in mathematics - irrational, complex and others. You learn about them in high school.
N.Ya.Vilenkin, A.S. Chesnokov, S.I. Shvartsburd, V.I. Zhokhov, Mathematics for grade 6, Textbook for high school
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The concept of numbers refers to abstractions that characterize an object from a quantitative point of view. Even in primitive society, people had a need to count objects, so numerical notations appeared. Later they became the basis of mathematics as a science.
To operate with mathematical concepts, it is necessary, first of all, to imagine what kind of numbers there are. There are several main types of numbers. This:
1. Natural - those that we get when numbering objects (their natural counting). Their set is denoted by N.
2. Integers (their set is denoted by the letter Z). This includes natural numbers, their opposites, negative integers, and zero.
3. Rational numbers (letter Q). These are those that can be represented as a fraction, the numerator of which is equal to a whole number, and the denominator is equal to a natural number. All are whole and classified as rational.
4. Real (they are designated by the letter R). They include rational and irrational numbers. Numbers obtained from rational numbers by various operations(calculating the logarithm, extracting the root), which themselves are not rational.
Thus, any of the listed sets is a subset of the following. This thesis is illustrated by a diagram in the form of the so-called. Euler circles. The design consists of several concentric ovals, each of which is located inside the other. The inner, smallest oval (area) denotes the set natural numbers. It is completely encompassed and includes the region symbolizing the set of integers, which, in turn, is contained within the region of rational numbers. The outer, largest oval, which includes all the others, denotes an array
In this article we will look at the set of rational numbers, their properties and features. As already mentioned, all existing numbers (positive, as well as negative and zero) belong to them. Rational numbers form an infinite series with the following properties:
This set is ordered, that is, by taking any pair of numbers from this series, we can always find out which one is larger;
Taking any pair of such numbers, we can always place at least one more between them, and, consequently, a whole series of them - thus, rational numbers represent an infinite series;
All four arithmetic operations on such numbers are possible, their result is always a certain number (also rational); the exception is division by 0 (zero) - it is impossible;
Any rational numbers can be represented as decimal fractions. These fractions can be either finite or infinitely periodic.
To compare two numbers belonging to the rational set, you need to remember:
Any positive number greater than zero;
Any negative number is always less than zero;
When comparing two negative rational numbers, the one whose absolute value (modulus) is smaller is greater.
How are operations performed with rational numbers?
To add two such numbers that have the same sign, you need to add their absolute values and put them in front of the sum general sign. To add numbers with different signs one should subtract the smaller one from the larger value and put the sign of the one whose absolute value is greater.
To subtract one rational number from another, it is enough to add the opposite of the second to the first number. To multiply two numbers, you need to multiply their values absolute values. The result obtained will be positive if the factors have the same sign, and negative if they are different.
Division is carried out in a similar way, that is, the quotient of absolute values is found, and the result is preceded by a “+” sign if the signs of the dividend and divisor coincide, and a “-” sign if they do not match.
Powers of rational numbers look like products of several factors that are equal to each other.
This article provides an overview properties of operations with rational numbers. First, the basic properties on which all other properties are based are announced. After this, some other frequently used properties of operations with rational numbers are given.
Page navigation.
Let's list basic properties of operations with rational numbers(a, b and c are arbitrary rational numbers):
- Commutative property of addition a+b=b+a.
- Combinative property of addition (a+b)+c=a+(b+c) .
- The existence of a neutral element by addition - zero, the addition of which with any number does not change this number, that is, a+0=a.
- For every rational number a there is an opposite number −a such that a+(−a)=0.
- Commutative property of multiplication of rational numbers a·b=b·a.
- Combinative property of multiplication (a·b)·c=a·(b·c) .
- The existence of a neutral element for multiplication is a unit, multiplication by which any number does not change this number, that is, a·1=a.
- For every non-zero rational number a there is an inverse number a −1 such that a·a −1 =1 .
- Finally, addition and multiplication of rational numbers are related by the distributive property of multiplication relative to addition: a·(b+c)=a·b+a·c.
The listed properties of operations with rational numbers are basic, since all other properties can be obtained from them.
Other important properties
In addition to the nine listed basic properties of operations with rational numbers, there are a number of very widely used properties. Let's give them short review.
Let's start with the property, which is written using letters as a·(−b)=−(a·b) or by virtue of the commutative property of multiplication as (−a) b=−(a b). The rule for multiplying rational numbers with different signs directly follows from this property; its proof is also given in this article. This property explains the rule “plus multiplied by minus is minus, and minus multiplied by plus is minus.”
Here is the following property: (−a)·(−b)=a·b. This implies the rule for multiplying negative rational numbers; in this article you will also find a proof of the above equality. This property corresponds to the multiplication rule “minus times minus is plus.”
Undoubtedly, it is worth focusing on multiplying an arbitrary rational number a by zero: a·0=0 or 0 a=0. Let's prove this property. We know that 0=d+(−d) for any rational d, then a·0=a·(d+(−d)) . The distribution property allows the resulting expression to be rewritten as a·d+a·(−d) , and since a·(−d)=−(a·d) , then a·d+a·(−d)=a·d+(−(a·d)). So we came to the sum of two opposite numbers, equal to a·d and −(a·d), their sum gives zero, which proves the equality a·0=0.
It is easy to notice that above we listed only the properties of addition and multiplication, while not a word was said about the properties of subtraction and division. This is due to the fact that on the set of rational numbers, the actions of subtraction and division are specified as the inverse of addition and multiplication, respectively. That is, the difference a−b is the sum of a+(−b), and the quotient a:b is the product a·b−1 (b≠0).
Given these definitions of subtraction and division, as well as the basic properties of addition and multiplication, you can prove any properties of operations with rational numbers.
As an example, let’s prove the distribution property of multiplication relative to subtraction: a·(b−c)=a·b−a·c. The following chain of equalities holds: a·(b−c)=a·(b+(−c))= a·b+a·(−c)=a·b+(−(a·c))=a·b−a·c, which is the proof.
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This lesson covers addition and subtraction of rational numbers. The topic is classified as complex. Here it is necessary to use the entire arsenal of previously acquired knowledge.
The rules for adding and subtracting integers also apply to rational numbers. Recall that rational numbers are numbers that can be represented as a fraction, where a – this is the numerator of the fraction, b is the denominator of the fraction. Wherein, b should not be zero.
In this lesson, we will increasingly call fractions and mixed numbers by one common phrase - rational numbers.
Lesson navigation:Example 1. Find the meaning of the expression:
Let's enclose each rational number in brackets along with its signs. We take into account that the plus given in the expression is an operation sign and does not apply to the fraction. This fraction has its own plus sign, which is invisible due to the fact that it is not written down. But we will write it down for clarity:
This is the addition of rational numbers with different signs. To add rational numbers with different signs, you need to subtract the smaller module from the larger module, and before the resulting answer put the sign of the rational number whose module is larger. And in order to understand which modulus is greater and which is smaller, you need to be able to compare the moduli of these fractions before calculating them:
The modulus of a rational number is greater than the modulus of a rational number. Therefore, we subtracted from . We received an answer. Then, reducing this fraction by 2, we got the final answer.
Some primitive actions, such as putting numbers in brackets and adding modules, can be skipped. This example can be written briefly:
Example 2. Find the meaning of the expression:
Let's enclose each rational number in brackets along with its signs. We take into account that the minus standing between rational numbers is a sign of the operation and does not apply to the fraction. This fraction has its own plus sign, which is invisible due to the fact that it is not written down. But we will write it down for clarity:
Let's replace subtraction with addition. Let us remind you that to do this you need to add to the minuend the number opposite to the subtrahend:
We obtained the addition of negative rational numbers. To add negative rational numbers, you need to add their modules and put a minus in front of the resulting answer:
Note. It is not necessary to enclose every rational number in parentheses. This is done for convenience, in order to clearly see which signs the rational numbers have.
Example 3. Find the meaning of the expression:
In this expression, the fractions have different denominators. To make our task easier, let's reduce these fractions to a common denominator. We will not dwell in detail on how to do this. If you experience difficulties, be sure to repeat the lesson.
After reducing the fractions to a common denominator, the expression will take the following form:
This is the addition of rational numbers with different signs. We subtract the smaller module from the larger module, and before the resulting answer we put the sign of the rational number whose module is greater:
Let's write down the solution to this example in short:
Example 4. Find the value of an expression
Let's calculate this expression as follows: add the rational numbers and, then subtract the rational number from the resulting result. 
First action:
Second action:
Example 5. Find the meaning of the expression:
Let's represent the integer −1 as a fraction, and convert the mixed number into an improper fraction:
Let's enclose each rational number in brackets along with its signs:
We obtained the addition of rational numbers with different signs. We subtract the smaller module from the larger module, and before the resulting answer we put the sign of the rational number whose module is greater:
We received an answer.
There is a second solution. It consists of putting whole parts together separately.
So, let's return to the original expression:
Let's enclose each number in parentheses. To do this, the mixed number is temporary:
Let's calculate the integer parts:
(−1) + (+2) = 1
In the main expression, instead of (−1) + (+2), we write the resulting unit:
The resulting expression is . To do this, write the unit and the fraction together:
Let's write the solution this way in a shorter way:
Example 6. Find the value of an expression
Let's convert the mixed number to an improper fraction. Let's rewrite the rest without changing:
Let's enclose each rational number in brackets along with its signs:
Let's replace subtraction with addition:
Let's write down the solution to this example in short:
Example 7. Find the value of an expression
Let's represent the integer −5 as a fraction, and convert the mixed number into an improper fraction:
Let's bring these fractions to a common denominator. After they are reduced to a common denominator, they will take the following form:
Let's enclose each rational number in brackets along with its signs:
Let's replace subtraction with addition:
We obtained the addition of negative rational numbers. Let’s add the modules of these numbers and put a minus in front of the resulting answer:
Thus, the value of the expression is .
Let's solve this example in the second way. Let's return to the original expression:
Let's write the mixed number in expanded form. Let's rewrite the rest without changes:
We enclose each rational number in brackets together with its signs:
Let's calculate the integer parts:
In the main expression, instead of writing the resulting number −7
The expression is an expanded form of writing a mixed number. We write the number −7 and the fraction together to form the final answer:
Let's write this solution briefly:
Example 8. Find the value of an expression
We enclose each rational number in brackets together with its signs:
Let's replace subtraction with addition:
We obtained the addition of negative rational numbers. Let’s add the modules of these numbers and put a minus in front of the resulting answer:
So the value of the expression is
This example can be solved in the second way. It consists of adding whole and fractional parts separately. Let's return to the original expression:
Let's enclose each rational number in brackets along with its signs:
Let's replace subtraction with addition:
We obtained the addition of negative rational numbers. Let's add the modules of these numbers and put a minus in front of the resulting answer. But this time we will add the whole parts (−1 and −2), both fractional and
Let's write this solution briefly:
Example 9. Find expression expressions 
Let's convert mixed numbers to improper fractions:
Let's enclose a rational number in brackets together with its sign. There is no need to put a rational number in parentheses, since it is already in parentheses:
We obtained the addition of negative rational numbers. Let’s add the modules of these numbers and put a minus in front of the resulting answer:
So the value of the expression is
Now let's try to solve this same example in the second way, namely by adding integers and fractional parts separately.
This time, in order to get a short solution, let's try to skip some steps, such as writing a mixed number in expanded form and replacing subtraction with addition:
Please note that fractional parts have been reduced to a common denominator.
Example 10. Find the value of an expression 
Let's replace subtraction with addition:
The resulting expression does not contain negative numbers, which are the main reason for errors. And since there are no negative numbers, we can remove the plus in front of the subtrahend and also remove the parentheses:
The result is a simple expression that is easy to calculate. Let's calculate it in any way convenient for us:
Example 11. Find the value of an expression
This is the addition of rational numbers with different signs. Let us subtract the smaller module from the larger module, and before the resulting answer we put the sign of the rational number whose module is greater:
Example 12. Find the value of an expression 
The expression consists of several rational numbers. According to, first of all you need to perform the steps in brackets.
First, we calculate the expression, then we add the obtained results.
First action:
Second action:
Third action:
Answer: expression value equals
Example 13. Find the value of an expression 
Let's convert mixed numbers to improper fractions:
Let's put the rational number in brackets along with its sign. There is no need to put the rational number in parentheses, since it is already in parentheses:
Let's bring these fractions to a common denominator. After they are reduced to a common denominator, they will take the following form:
Let's replace subtraction with addition:
We obtained the addition of rational numbers with different signs. Let us subtract the smaller module from the larger module, and before the resulting answer we put the sign of the rational number whose module is greater:
Thus, the meaning of the expression equals
Let's look at adding and subtracting decimals, which are also rational numbers and can be either positive or negative.
Example 14. Find the value of the expression −3.2 + 4.3
Let's enclose each rational number in brackets along with its signs. We take into account that the plus given in the expression is an operation sign and does not apply to the decimal fraction 4.3. This decimal fraction has its own plus sign, which is invisible due to the fact that it is not written down. But we will write it down for clarity:
(−3,2) + (+4,3)
This is the addition of rational numbers with different signs. To add rational numbers with different signs, you need to subtract the smaller module from the larger module, and before the resulting answer put the rational number whose module is larger. And in order to understand which module is larger and which is smaller, you need to be able to compare the modules of these decimal fractions before calculating them:
(−3,2) + (+4,3) = |+4,3| − |−3,2| = 1,1
The modulus of the number 4.3 is greater than the modulus of the number −3.2, so we subtracted 3.2 from 4.3. We received the answer 1.1. The answer is positive, since the answer must be preceded by the sign of the rational number whose modulus is greater. And the modulus of the number 4.3 is greater than the modulus of the number −3.2
Thus, the value of the expression −3.2 + (+4.3) is 1.1
−3,2 + (+4,3) = 1,1
Example 15. Find the value of the expression 3.5 + (−8.3)
This is the addition of rational numbers with different signs. As in the previous example, we subtract the smaller one from the larger module and before the answer we put the sign of the rational number whose module is greater:
3,5 + (−8,3) = −(|−8,3| − |3,5|) = −(8,3 − 3,5) = −(4,8) = −4,8
Thus, the value of the expression 3.5 + (−8.3) is −4.8
This example can be written briefly:
3,5 + (−8,3) = −4,8
Example 16. Find the value of the expression −7.2 + (−3.11)
This is the addition of negative rational numbers. To add negative rational numbers, you need to add their modules and put a minus in front of the resulting answer.
You can skip the entry with modules so as not to clutter the expression:
−7,2 + (−3,11) = −7,20 + (−3,11) = −(7,20 + 3,11) = −(10,31) = −10,31
Thus, the value of the expression −7.2 + (−3.11) is −10.31
This example can be written briefly:
−7,2 + (−3,11) = −10,31
Example 17. Find the value of the expression −0.48 + (−2.7)
This is the addition of negative rational numbers. Let's add their modules and put a minus in front of the resulting answer. You can skip the entry with modules so as not to clutter the expression:
−0,48 + (−2,7) = (−0,48) + (−2,70) = −(0,48 + 2,70) = −(3,18) = −3,18
Example 18. Find the value of the expression −4.9 − 5.9
Let's enclose each rational number in brackets along with its signs. We take into account that the minus, which is located between the rational numbers −4.9 and 5.9, is an operation sign and does not belong to the number 5.9. This rational number has its own plus sign, which is invisible due to the fact that it is not written down. But we will write it down for clarity:
(−4,9) − (+5,9)
Let's replace subtraction with addition:
(−4,9) + (−5,9)
We obtained the addition of negative rational numbers. Let’s add their modules and put a minus in front of the resulting answer:
(−4,9) + (−5,9) = −(4,9 + 5,9) = −(10,8) = −10,8
Thus, the value of the expression −4.9 − 5.9 is −10.8
−4,9 − 5,9 = −10,8
Example 19. Find the value of the expression 7 − 9.3
Let's put each number in brackets along with its signs.
(+7) − (+9,3)
Let's replace subtraction with addition
(+7) + (−9,3)
(+7) + (−9,3) = −(9,3 − 7) = −(2,3) = −2,3
Thus, the value of the expression 7 − 9.3 is −2.3
Let's write down the solution to this example in short:
7 − 9,3 = −2,3
Example 20. Find the value of the expression −0.25 − (−1.2)
Let's replace subtraction with addition:
−0,25 + (+1,2)
We obtained the addition of rational numbers with different signs. Let us subtract the smaller module from the larger module, and before the answer we put the sign of the number whose module is greater:
−0,25 + (+1,2) = 1,2 − 0,25 = 0,95
Let's write down the solution to this example in short:
−0,25 − (−1,2) = 0,95
Example 21. Find the value of the expression −3.5 + (4.1 − 7.1)
Let's perform the actions in brackets, then add the resulting answer with the number −3.5
First action:
4,1 − 7,1 = (+4,1) − (+7,1) = (+4,1) + (−7,1) = −(7,1 − 4,1) = −(3,0) = −3,0
Second action:
−3,5 + (−3,0) = −(3,5 + 3,0) = −(6,5) = −6,5
Answer: the value of the expression −3.5 + (4.1 − 7.1) is −6.5.
Example 22. Find the value of the expression (3.5 − 2.9) − (3.7 − 9.1)
Let's do the steps in parentheses. Then, from the number that was obtained as a result of executing the first brackets, subtract the number that was obtained as a result of executing the second brackets:
First action:
3,5 − 2,9 = (+3,5) − (+2,9) = (+3,5) + (−2,9) = 3,5 − 2,9 = 0,6
Second action:
3,7 − 9,1 = (+3,7) − (+9,1) = (+3,7) + (−9,1) = −(9,1 − 3,7) = −(5,4) = −5,4
Third act
0,6 − (−5,4) = (+0,6) + (+5,4) = 0,6 + 5,4 = 6,0 = 6
Answer: the value of the expression (3.5 − 2.9) − (3.7 − 9.1) is 6.
Example 23. Find the value of an expression −3,8 + 17,15 − 6,2 − 6,15
Let us enclose each rational number in brackets along with its signs
(−3,8) + (+17,15) − (+6,2) − (+6,15)
Let's replace subtraction with addition where possible:
(−3,8) + (+17,15) + (−6,2) + (−6,15)
The expression consists of several terms. According to the combinatory law of addition, if an expression consists of several terms, then the sum will not depend on the order of actions. This means that the terms can be added in any order.
Let's not reinvent the wheel, but add all the terms from left to right in the order they appear:
First action:
(−3,8) + (+17,15) = 17,15 − 3,80 = 13,35
Second action:
13,35 + (−6,2) = 13,35 − −6,20 = 7,15
Third action:
7,15 + (−6,15) = 7,15 − 6,15 = 1,00 = 1
Answer: the value of the expression −3.8 + 17.15 − 6.2 − 6.15 is 1.
Example 24. Find the value of an expression
Let's translate decimal−1.8 in a mixed number. Let's rewrite the rest without changing:
