Page 13 - Maths Skills - 7

Integers 11

Let’s Attempt

Example 1: Solve.
(i) 9 – (– 4) (ii) 14 – (–5) (iii) (– 25) – (– 14) (iv) (– 12) – (4)

Solution: (i) 9 – (– 4) = 9 + (4) = 13 (ii) 14 – (– 5) = 14 + (5) = 19
(iii) (– 25) – (– 14) = (– 25) + (14) = – 11 (iv) (– 12) – (4) = – 12 + (– 4) = – 16

Example 2: In a quiz, positive marks are given for correct answer and negative marks are given for incorrect
answer. If Jack’s score in five successive rounds were 25, – 5, – 10, 15 and 10, what was his total
marks at the end?
Solution: Jack’s score at the end will be = Sum of the total marks secured in five successive rounds
= 25 + (–5) + (– 10) + (15) + 10
= 20 + (– 10) + 15 + 10 = 10 + 15 + 10 = 35

Example 3: A plane is flying at the height of 5000 m above the sea level. At a particular point it is
exactly above a submarine floating 1200 m below the sea level. What is the vertical distance
between them?
Solution: Let A be the position of aeroplane above the sea level and B A
be the position of submarine below the sea level. + 5000 m
The vertical distance O Sea level

AB = | AO | + | BO = 5000 + | – 1200 | – 1200 m
= 5000 + 1200 = 6200 m B

Example 4: (i) Write a pair of negative integers whose difference is 5.

(ii) Write a negative integer and a positive integer whose sum is – 3.
(iii) Write a negative integer and a positive integer whose difference is – 3.

Solution: (i) – 5 and – 10, Q – 5 – (– 10) = – 5 + 10 = 5 Absorbing Facts

(ii) – 8 and 5, Q – 8 + 5 = – (8 – 5) = – 3 There are infinite pairs of integers

(iii) – 2 and + 1, Q – 2 – (+1) = – 2 – 1 = – 3 satisfying the above cases.

Exercise 1.2

1. Add the following.
(i) 459 + (–265) (ii) – 873 + 276 (iii) – 65 + (–77) (iv) – 393 + 643

2. Subtract the following.
(i) 465 from –289 (ii) –135 from –895 (iii) –1018 from 1018 (iv) 0 from –2095
3. Simplify the following.

(i) [16 – (–2) + (–23 –17)] (ii) –119 + [(–63) – 74]
(iii) [85 – (–9)] + [( –61) –33] (iv) 48 + [(–35) – 63] – (–119)