Class 7 Maths NCERT Solutions for Chapter 1 Integers Chapter 1 Integers EX – 1.2

Integers

Question 1.
Write down a pair of integers whose:
(a)
 The sum is – 7
(b) Difference is -10
(c) Sum is 0

Solution.
(a) A pair of integers whose sum is – 7 can be (- 1) and (- 6).
∵ (- 1) + (- 6) = – 7
(b) A pair of integers whose difference is -10 can be (- 11) and (- 1)
∵ – 11 – (- 1) = – 11 + 1 = – 10
(c) A pair of integers whose sum is 0 can be 1 and (- 1).
∵ (- 1) + (1) = 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.

Solution.
(a) A pair of negative integers whose difference gives 8 can be – 12 and – 20.
∵ (-12) – (- 20) = -12 + 20 = 8 .
(b) A negative integer and a positive integer whose sum is -5 can be – 13 and 8.
∵ (- 13) + 8 = -13 + 8 = – 5
(c) A negative integer and a positive integer whose difference is -3 can be – 1 and 2.
∵ (- 1) – 2 = – 1 – 2 = – 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?

Solution.
Total scores of team A = (- 40) + 10 + 0
= – 40 + 10 + 0 = – 30
and, total scores of team B = 10 + 0 + (- 40)
= 10 + 0 – 40 = – 30
Since the total scores of each team are equal.
∴ No team scored more than the other but each has an equal score.
Yes, integers can be added in any order and the result remains unaltered. For example, 10 + 0 + (- 40) = – 30 = – 40 + 0 + 10

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] + ……

Solution.
(i) (- 5) + (- 8) = (- 8) + (- 5)
(ii) – 53 + 0 = – 53
(iii) 17 + (-17) = 0
(iv) [13 + (- 12)] + (- 7) = (13) + [(- 12) + (- 7)]
(v) (- 4) + [15 + (- 3)] = [(- 4 ) + 15] + (- 3)

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