Subtraction of Integers

 

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When Integers need to be subtracted, we need to change the sign of the integer to be subtracted and then add.

Demonstration:

(i) Subtract: +6 from +9

(+9) – (+6)

Here the +6 is subtracted from +9

= +9 – 6, [(+6) changes to (-6)]

Now add +9 and -6 using the addition of integers rule.

= +3

(ii) Subtract: -16 from -46

(-45) – (-15)

Here the -15 is subtracted from -45

= -45 + 15, [(-15) changes to (+15)]

Now add -45 and +15 using the addition of integers rule.

= -30

When the integers have ‘unlike signs’ that is, one is positive and the other is negative, even the addition operation becomes subtraction.

Demonstration:

(i) Add: + 47 and -27

The absolute values of +47 and -27 are 47 and 27 respectively;

and their difference = 47 – 27 = 30.

Since, the integers with greater absolute value is 47 and its sign is ‘+’

Therefore, (+47) + (-27) = +30

(ii) Add: -66 and +24

The absolute values of -66 and +24 are 66 and 24 respectively;

and their difference = 66 - 24 = 42.

Since, the integers with greater absolute value is 66 and it sign is ‘-’

Therefore, (-66) + (+24) = -42