## Math 6 Chapter 2 Lesson 5: Add two integers with different signs

## 1. Summary of theory Tóm

Two opposite integers whose sum is 0.

– To add two integers with opposite signs, we find the difference between their two absolute values (large number minus small number) and then put in front of the result to find the sign of the number with the larger absolute value.

## 2. Illustrated exercise

**Question 1: **Calculate (-273) + 55

__Solution guide__

(-273) + 55

= – (273 – 55) (because 273 > 55)

= -218

**Verse 2: **The temperature in the chilled room in the morning is 3^{0}C, the afternoon of the same day fell 5^{0}C. What was the temperature in the chilled room that afternoon?

__Solution guide__

5 . off^{0}C means increase -5^{0}C, so we need to calculate: (+3) + (-5) = ?

(+3) + (-5) = -2

**Question 3: **Calculate and compare the results of

a. 37 + (-27) and (-27) + 37

b. 16 + (-16) and (-105) + 105

__Solution guide__

a. 37 + (-27) and (-27) + 37

37 + (-27) = 10

(-27) + 37 = 10

37 + (-27) = (-27) + 37

b. 16 + (-16) and (-105) + 105

16 + (-16) = 0

(-105) + 105 = 0

16 + (-16) = (-105) + 105

## 3. Practice

### 3.1. Essay exercises

**Question 1:** Write the next two numbers in each of the following series

a. -4, -1, 2,… (the latter term is 3 units larger than the previous term)

b. 5, 1, -3,…. (the latter term is 4 units smaller than the previous term)

**Verse 2:** Calculate the value of the expression

a. a + (-25), know a = -15

b. (-87) + b, know b = 13

**Question 3: **Write the number (-17) as the sum of two integers

a. Same sign

b. Same sign and absolute value of each number is greater than 5

c. Different sign and absolute value of each number is less than 20.

### 3.2. Multiple choice exercises Bài

**Question 1: **Choose the wrong statement?

A. Two opposite integers whose sum is 0

B. -5 + 4 = -1

C. Two opposite integers whose sum is 1

D. |-5| -|-12| = -7

**Verse 2: **The value of the expression: (-40) + (-5) + 15 is:

A. -30

B. -20

C. 60

D. 50

**Question 3: **Find x, knowing that x + (-5) = -16

A. 21

B. 11

C. -21

D. -11

**Question 4: **Find an integer a knowing that a is less than 2 unit years

A. -2

B. -3

C. -4

D. -5

**Question 5: **The Pythagorean mathematician was born in 570 BC. Vietnamese mathematician Luong The Vinh was born 2011 years after Pythagoras. What year was Mr. Luong The Vinh born?

A. -1441

B. 1144

C. 1441

D. -1144

## 4. Conclusion

Through this lesson Add two integers with different signs, you need to complete some of the objectives given by the lesson such as:

- Master the rule of adding two integers with different signs
- Apply the rule to do some exercises related to adding two integers with different signs

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