powers - anyone know how to do this?

[gmat_killer]

Which of the following is equal to 5^17 x 4^9?

A) 2 x 10^13
B) 2 x 10^17
C) 2 X 10^20
D) 2 x 10^26
E) 2 x 10^36

Thanks!

[cramya]

4= 2^2

5^17 x (2^2)^9 ( (a^b)^c = a^ (b*c) where a=2 b=2 c=9)

5^17 * 2 ^18

5^17 * 2^17 * 2^1 ( 10^17 can be split as (2*5) ^17 = 2^17 * 5^17)

10^17 * 2

B

[truplayer256]

5^17*4^9

5^17*(2^2)^(9)

5^17*2^18

5^17*2^17*2

(10^17)*2 B.