Exponent ? - GMATPrep

[djsir007]

5^21X4^11 = 2X10^n what is n?

[jayhawk2001]

5^21 X 4^11 = 2X10^n what is n?

5 * 5^20 * 4 * 4^10 = 2* 10^n
20 * 5^20 * 2^20 = 20 * 10^(n-1)
20 * 10^20 = 20 * 10^(n-1)

n-1 = 20
n = 21

[djsir007]

is 4^10 = 2^20

is this the only set of numbers that you can swap like this?

Thank you for the help?

[jayhawk2001]

is 4^10 = 2^20

is this the only set of numbers that you can swap like this?

Thank you for the help?

Rule of thumb is (x^y)^z = x^(y*z)

So, 4^10 = (2^2)^10 = 2^20

[Cybermusings]

dude this has been posted in an old thread...please check the old posts before posting new ones, since the questions criculating become repititive

[ns88]

5^21 (4^11) =2 (10^n)

let's work with 2 (10^n)

2 (5^n) (2^n)

5^n (2^n+1)

5^n (4^((n+1)/2)

n=21