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 Post subject: GMAT Number Theory
PostPosted: Mon Dec 06, 2010 2:27 pm 
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Joined: Sun May 30, 2010 3:15 am
Posts: 424
The product of the squares of two positive integers is 100. How many pairs of positive integers satisfy this condition?

A. 0
B. 1
C. 2
D. 3
E. 4

(C) 100 = 2 × 2 × 5 × 5.

The only possible combination of the prime factors that make the product of two squares is 2² × 5² = 100. Besides, 100 is the square of the positive integer itself so 10² × 1² = 100.

There are two possible pairs of positive integers that satisfy the condition:
(1, 10) and (2, 5).

The correct answer is choice (C).
-------------

The answer is wrong. The product of the squares of two other positive inegers is also 100: 8 & 6. 64 + 36=100.


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 Post subject: Re: GMAT Number Theory
PostPosted: Mon Dec 06, 2010 2:29 pm 
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Joined: Sun May 30, 2010 2:23 am
Posts: 498
The product of 8² and 6² does NOT equal 100.
8² × 6² = 64 × 36 = 2304.


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