Page 29 - Maths Skill - 6

The Other Side of Zero 27

Example 2: Find the sum of: (i) 372 and – 543 (ii) – 500, 100 and 325

Solution: (i) 372 + (– 543) = – (543 – 372) = – 171
(ii) – 500 + 100 + 325 = –500 + (100 + 325) = – 500 + 425 = – (500 – 425) = – 75
Example 3: Write additive inverse of the following:

(i) 0 (ii) – 25 (iii) 70
Solution: (i) 0 + 0 = 0 Therefore, additive inverse of zero is 0.

(ii) – 25 + 25 = 0 Therefore, +25 is the additive inverse of –25
(iii) 70 + (– 70) = 0 Therefore, – 70 is the additive inverse of 70
Example 4: Find the sum of: (– 20) + (+ 50) + (– 60) + (+ 30).

Solution: We arrange the numbers so that, the positive integers and negative integers are grouped together.
We have, (– 20) + (– 60) + (+ 50) + (+ 30) = (– 80) + (+ 80) = 0
Example 5: Find the value of (– 28) + (– 17) + (– 68) + (+ 55) + (85).

Solution: Group the positive and the negative integers together,
(– 28) + (– 17) + (– 68) + (55) + (85) = (– 113) + (140) = + (140 – 113) = 27
Example 6: Find the sum of –288, 49 and 226.

Solution: (– 288) + (49) + (226) = (– 288) + (275) = – 13

Exercise 2.2

1. Add the following integers, using a number line:

(i) 9 + (– 3) (ii) 5 + (– 11) (iii) (– 1) + (– 4)

(iv) (– 5) + 12 (v) (– 1) + (– 2) + (– 4) (vi) (– 2) + 4 + (– 5)
2. Add without using a number line:

(i) 155 + (– 175) (ii) 933 + (– 33) (iii) (– 525) + (– 75)

(iv) (– 391) + (91) + (– 150) (v) 1262 + (– 366) + (– 962) (vi) (– 560) + (160)
3. Fill in the suitable integer in the box.

(i) 7 + = 0 (ii) + 5 = 0 (iii) – 20 + = 0

(iv) + (– 9) = 0 (v) 4 + = 0 (vi) + 0 = 0

4. A shopkeeper had a profit of ` 130 on Monday, a loss of ` 65 on Tuesday and a loss of ` 53 on Wednesday.
Find his net profit or loss in these three days.

(Hint: Indicate profit by positive integer and loss by negative integer)
5. Replace by >, < or =.

(i) (– 7) + (– 3) (– 9) + (4) (ii) (– 15) + (14) (– 17) + (– 11)

(iii) (– 27) + (– 22) (– 24) + (– 25) (iv) (90) + (– 40) (– 40) + (70)