If the length of each edge in a cube is increased by the

Question

If the length of each edge in a cube is increased by the same percent and the result was that the cube had 25% more volume than it originally had, by what percentage were the edges increased?
(A)  \sqrt {25%} 
(B) 5%
(C) 7.7%
(D) 8.33%
(E) 12.5%

jallenmorris · Answer

can you show your work? (i.e., how did you get that answer?)

spiridon · Answer

used plug ins (deduction)

figured would be easier then to try algebraic solution so..

original cube 10x10x10=1000 volume
increased side by (pick C) 10*1.077=10.77
10.77*10.77*10.77=1250 volume

compare volumes and get 25% increase

is that right?

jallenmorris · Answer

I think it's right. I did use number picking too.

I used volume of the original cube is 8 (because it's a cube of 2) and increase that by 25% gives us a new volume of 10.

To find one side of the larger cube, it's the cube root of 10 divided by 2 because 2 was the original length of one side of the cube.

\sqrt {10}/2 = 1.077 , because the question asks for the amount of increase, we subtract 1 from this value and get .077, or 7.7%. I don't have the OA, but it seems to be right to me. We each used different numbers and came up with the same answer. Most likely true.

If the length of each edge in a cube is increased by the

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