Integers - Solutions 2

CBSE Class –VII Mathematics
NCERT Solutions
Chapter 1 Integers (Ex. 1.2)

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Question 1. Write down a pair of integers whose:

(a) sum is -7     (b) difference is -10     (c) sum is 0

Answer: (a) One such pair whose sum is -7 : ( -5, -2) (-10, 3)

(b) One such pair whose difference is -10:  (-2, 8 ), (-11, -1)

(c) One such pair whose sum is 0: (5,5) ,(6,6)

Question 2. (a) Write a pair of negative integers whose difference gives 8.
(b) Write a negative integer and a positive integer whose is  -5.
(c) Write a negative integer and a positive integer whose difference is -3.

Answer: (a) (-2, -10) (-5, -13)

(b) ( -7, 2), ( -9,4)

(c) ( -1, 2), ( -2, 1) 

Question 3. In a quiz, team A scored -40,10, 0 and team B scores 0, 10, -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 of Team A = -40+10+0 = -30

Team B scored 0, 10, -40

Total score of Team B = 0+10 +(-40) =  0+10 - 40 =  -30

Thus, scores of both teams are same.

Yes, we can add integers in any order due to commutative property.

Question 4. Fill in the blanks to make the following statements true:

(i)(−5)+(−8)=(−8)+(.......)$\left(-5\right)+\left(-8\right)=\left(-8\right)+\left(.......\right)$

(ii)−53+.......=−53$-53+.......=-53$

(iii)17 + ……. = 0

(iv)[13+(−12)]+(.......)=13+[(−12)+(−7)]$\left[13+\left(-12\right)\right]+\left(.......\right)=13+\left[\left(-12\right)+\left(-7\right)\right]$

(v)(−4)+[15+(−3)]=[−4+15]+.......$\left(-4\right)+\left[15+\left(-3\right)\right]=\left[-4+15\right]+.......$

Answer: (i) (−5)+(−8)=(−8)+(−5)−−−−$\left(-5\right)+\left(-8\right)=\left(-8\right)+\underset{\_}{\left(-5\right)}$ [Commutative property]

(ii) −53+0–=−53$-53+\underset{\_}{0}=-53$ [Zero additive property]

(iii) 17+(−17)−−−−−=0$17+\underset{\_}{\left(-17\right)}=0$ (Additive identity]

(iv)[13+(12)]+(−7)−−−−=13+[(−12)+(−7)]$\left[13+\left(12\right)\right]+\underset{\_}{\left(-7\right)}=13+\left[\left(-12\right)+\left(-7\right)\right]$ [Associative property]

(−4)+[15+(−3)]=[−4+15]+(−3)−−−−$\left(-4\right)+\left[15+\left(-3\right)\right]=\left[-4+15\right]+\underset{\_}{\left(-3\right)}$ [Associative property]