Integers Class 7 Mathematics Chapter 1 Exercise 1.2 : NCERT Solution
1. Write down a pair of integers whose :
(a) sum is -7
(b) difference is -10
(c) sum is 0
Solution :
(a) (-4) + (-3) = -7
(b) 10 - 20 = -10
(c) (-1) + 1 = 0
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 :
One such pair could be :
(a) -2, -10; [-2-(-10) = 8]
(b) -6, 1 [-6 + 1 = -5]
(c) -1, 2; (-1 -2 = -3)
3. In q 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 score of team A
= -40 + 10 + 0
= -30
Total score of team B
= 10 + 0 + (-40)
= 10 + 0 - 40
= -30
∴ The scores of both team are same i.e., -30
Yes, we can add the integers in any order.
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) [commutative law of additions]
(ii) -53 + 0 = -53 [Additive identity]
(iii) 17 + (-17) = 0 [Additive inverse]
(iv) [13 + (-12)] + (-7) = 13 + [(-12) + (-7)] [Associative law of addition]
(v) (-4) + [15 + (-3)] = [-4 + 15] + (-3) [Associative law of addition]