Page 123 - ICSE Math 5

Example 18: Subtract (–3) from (–5).
Solution: (–5) – (–3) = ? (Here, the subtrahend = –5 and the minuend = –3.)
Move 5 steps to the left of 0 to reach –5. Since the minuend is a negative integer,
start from –5 and move 3 steps to the right of –5 to reach –2.

–10 –9 –8 –7 –6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 7 8 9 10

So, (–5) – (–3) = –2.

Subtraction of Integers without Using a Number Line

To subtract integers without using a number line, we follow the given steps.
• Keep the sign of the subtrahend or the first integer as it is.

• Change the sign of the minuend or the second integer. For example, if the minuend or
second integer is positive, change it to negative and vice versa.
Example 19: Subtract the following integers (a) 7 from 6 and (b) –19 from –11.
Solution: (a) 7 from 6 (b) –19 from –11

6 – (+7) = 6 – 7 = –1 –11 – (–19) = –11 + 19 = 8

Exercise 8.4

1. Subtract the following integers using a number line.

(a) 5 from –8 (b) 9 from 10 (c) –6 from 0 (d) –6 from –8
2. Subtract the following integers without using a number line.

(a) 20 from 40 (b) –17 from 23 (c) –4 from –7 (d) 7 from –14

3. Find the following.
(a) (–5) – (+6) (b) 40 – (–30) (c) 67 – (+17) (d) –54 – (–45)

Review Exercise

1. Represent –10, –8, 0, 4 and 6 on a number line.

2. Look at the given number line representing integers and answer the following questions.
E D A C B F

(a) If letter A represents 0, then which letter represents –5?

(b) What does letter B represent: a negative integer or a positive integer?
(c) Write the integers represented by letters C and E.

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