If radius of sphere is decreased by 24%. By what per cent

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If radius of sphere is decreased by 24%. By what per cent does the surface area decrease ?

1. 44%
2. 49%
3. 42.24%
4. 46.2%

Correct Option: C

The decrease in volume is given [ x + y + xy/100 ] %
Here , x = y = -24
= [(-24) + (-24) + (-24) x (-24)/100] %
= [-48 + 576/100] % = -48 + 5.76 = - 42.24 %
(-ve sign denotes decrease in volume)