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Re: what is the value of b? [#permalink]
04 Feb 2012, 14:50
straight B. 36 = 2 ^2 * 3^2
If 3^a*4^b = c, what is the value of b?
Note that we are not told that the variables are integers only.
(1) 5^a = 25 --> a=2, but we can not get the values of b. Not sufficient.
(2) c = 36 --> 3^a*4^b = c: it's tempting to write 3^2*4^1=36 and say that b=1 but again we are not told that the variables are integers only. So, for example it can be that 3^a=36 for some non-integer a and b=0, making 4^b equal to 1 --> 3^a*4^b =36*1=36. Not sufficient.
(1)+(2) As a=2 and c = 36 then 9*4^b=36 --> b=1. Sufficient.