UPSC 2014 CDS II Math Paper

Let the side of the original cube = a units
Surface area of the original cube =6a2 square units
Side of the new cube =a+

100

100

×a=2aunits
Surface area of the new cube =6(2a2)=24a2square units
∴ % Increase in the surface areaTrick :
By x+y+

xy

100

, we get
100+100+

100×100

100

=300%