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OG MATH 241

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OG MATH 241

by resilient » Tue Feb 05, 2008 9:13 pm
IF THE INTEGER N HAS EXACTLY THREE DIVISORS, INCLUDING 1 AND N, HOW DIVISORS DOES N^2 HAVE?

A. 4
B. 5
C.6
D.8
E.9



QA IS B.... my question what is the best way of approaching monster questions like this when you are totaly lost. I tried to pick numbers and it got pretty messy
Appetite for 700 and I scraped my plate!
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Re: OG MATH 241

by Neo2000 » Tue Feb 05, 2008 11:37 pm
Enginpasa1 wrote: QA IS B.... my question what is the best way of approaching monster questions like this when you are totaly lost. I tried to pick numbers and it got pretty messy
Think of numbers that would satisfy this condition. And start small

You know 2 is prime. So it will have only 2 factors, 1 and itself
3 also is prime. Same as above.
4 is the square of 2. So it will have factors 1, 2 and itself

Voila! It matches. So are we looking for squares??

Check with 9. 1,3 and itself. So yes, Squares it is!

If you square 4 you will get 16.
Factors of 16 are 1, 2,4, 8 and 16 itself => 5factors
If you square 9 you will get 81
Factors are 1,3,9,27 and 81 =>5 factors again.

So your answer is 5
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