Answer :

plug in numbers. if originally, it was V=1/2 * 1 * 1 * 2=1 

tripling the dimensions would be V=1/2 * 3 * 3 * 6=27 

it would be 27 times larger. this could also be found by 3^3, just as doubling would render 2^3
The volume is 27ed. Three dimensions are tripled. 3x3x3=27.