If each side of a cube is decreased by 19 %, then decrease

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If each side of a cube is decreased by 19 %, then decrease in surface area of cube is ?

1. 40.4%
2. 38.4%
3. 35.6%
4. 34.39%

Correct Option: D

The net decrease in the surface area of the cube is given by
[x + y + xy/100] %
Here, x = y = 19%
= [-19 + (-19) + (-19) x (-19)/100] %
= [-38 + 361/100] %
= [-38 + 3.61] %= -34.39% (-ve sign implies for decrease)