Exponents - GMATPrep

[diegoasaavedra]

If 5^21 x 4^11 = 2 x 10^n what is the value of n?

a- 11
b- 21
c- 22
d- 23
e- 32

Answers is B, but I don't remember how to do it.

Thanks

[jayhawk2001]

If 5^21 x 4^11 = 2 x 10^n what is the value of n?

a- 11
b- 21
c- 22
d- 23
e- 32

Answers is B, but I don't remember how to do it.

Thanks

5^21 * 4^11
= 5^21 * 2^22
= 2 * 5^21 * 2^21
= 2 * 10^21

Hence B