Math questions from any Manhattan Prep GMAT Computer Adaptive Test.
alecm666
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Power Factors

by alecm666 Sun Apr 19, 2015 3:06 am

How many factors does 36^2 have? (CAT questions)
the answer is 25.


I want to know why we use primes to solve the problem? Because my math is really basic and dont know anything about primes' application expect its definition.

If let say the question is : how many factors does 22^2 have?
Should the answer be:
(11 * 2)^2
= 11, 11, 2 , 2
I can have zero to three 11; same for 2. So the answer is 3*3 = 9?
RonPurewal
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Re: Power Factors

by RonPurewal Sun Apr 26, 2015 3:07 am

alecm666 Wrote:If let say the question is : how many factors does 22^2 have?
Should the answer be:
(11 * 2)^2
= 11, 11, 2 , 2
I can have zero to three 11; same for 2. So the answer is 3*3 = 9?


yes, exactly.

if this is still uncomfortably abstract for you, you can actually list out the factors thus formed:
none of either = 1
2 = 2
2•2 = 4
11 = 11
2•11 = 22
2•2•11 = 44
11•11 = 121
2•11•11 = 242
2•2•11•11 = 484 {= the original number 22^2)

of course, it's not necessary to do this-- in fact, you don't even need to know that the original number is 484!-- but it may be edifying.