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NCERT solution class 7 chapter 1 Integers 1.2 mathematics

EXERCISE 1.2


Page No 9:

Question 1:

Write down a pair of integers whose:

(a) sum is − 7

(b) difference is − 10

(c) sum is 0

Answer:

(a) − 8 + (+1) = −7

(b) − 12 − (−2) = −10

(c) 5 + (−5) = 0

Question 2:

(a) Write a pair of negative integers whose difference gives 8.

(b) Write a negative integer and a positive integer whose sum is − 5.

(c) Write a negative integer and a positive integer whose difference is − 3.

Answer:

(a) −2 − (−10) = 8

(b) −8 + 3 = −5

(c) −2 − (+1) = −3

Question 3:

In a quiz, team A scored − 40, 10, 0 and team B scored 10, 0 − 40 in three successive rounds. Which team scored more? Can we say that we can add integers in any order?

Answer:

Team A scored − 40, 10, 0.

Total score = − 40 + 10 + 0

= −30

Team B scored 10, 0, −40.

Total score = 10 + 0 + (−40)

= −30

∴ The scores of both teams are equal.

Yes, we can add integers in any order. We had observed that the scores obtained by both teams in successive rounds were numerically equal but different in order. Yet, the total score of both teams were equal.

Question 4:

Fill in the blanks to make the following statements true:

(i) (− 5) + (− 8) = (− 8) + (…)

(ii) − 53 + … = − 53

(iii) 17 + … = 0

(iv) [13 + (− 12)] + (…) = 13 + [(− 12) + (− 7)]

(v) (− 4) + [15 + (− 3)] = [(− 4) + 15] +

Answer:

(i) 

(ii) 

(iii) 

(iv) 

(v) 

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