NCERT Class 7 Maths Chapter 1 Integers Exercise 1.2

Chapter 1 Integers Exercise 1.2

Question 1: Write down a pair of integers whose:
(a) sum is -7
Answer:
= -7 + 0
= -7

(b) difference is – 10
Answer:
= -25 - (-15)
= – 25 + 15
= -10

(c) sum is 0
Answer:
= 4 + (-4)
= 4 - 4
= 0

Question 2: (a) Write a pair of negative integers whose difference gives 8
Answer:
= (-5) - (- 13)
= -5 + 13
= 8

(b) Write a negative integer and a positive integer whose sum is – 5.
Answer:
= -25 + 20
= -5

(c) Write a negative integer and a positive integer whose difference is – 3.
Answer:
= -6 - (-3)
= -6 + 3
= -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:
Score of team A = -40, 10, 0
Score of team B = 10, 0, -40
Total score obtained by team A = ?
Total score obtained by team B = ?
Team A score = -40 + 10 + 0
= -30
Team B score = 10 + 0 + -40
= -30
Therefore, the score of the both A team and B team is same. Yes, we can say that we can add integers in any order.

Question 4: Fill in the blanks to make the following statements true:
(i) (-5) + (-8) = (-8) + (_)
Answer:
Let the unknown integer be x.
= (-5) + (-8) = (-8) + (x)
= -5 - 8 = -8 + x
= -13 = -8 + x
= -13 + 8 = x
= x = -5

(ii) –53 + _ = –53
Answer:
Let unknown integer be x.
= -53 + x = -53
= x = -53 + 53
= x = 0

(iii) 17 + _ = 0
Answer:
Let unknown integer be x.
= 17 + x = 0
= x = 0 – 17
= x = – 17

(iv) [13 + (– 12)] + (_) = 13 + [(–12) + (–7)]
Answer:
Let the unknown integer be x.
= [13 + (-12)] + (x) = 13 + [(-12) + (-7)]
= [13 - 12] + (x) = 13 + [-12 - 7]
= [1] + (x) = 13 + [-19]
= 1 + (x) = 13 - 19
= 1 + (x) = -6
= x = -6 - 1
= x = -7

(v) (– 4) + [15 + (–3)] = [– 4 + 15] + _
Answer:
Let the unknown integer be x.
= (-4) + [15 + (-3)] = [- 4 + 15] + x
= (-4) + [15 - 3)] = [- 4 + 15] + x
= (-4) + [12] = [11] + x
= 8 = 11 + x
= 8 - 11 = x
= x = -3