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GMATPrep factoring question

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GMATPrep factoring question

by allenkt » Sun May 06, 2007 5:37 pm
This one has me stumped. I know the answer should be 10 but I just can't seem to figure it out. Someone please show me how to solve this one!

1001^2 - 999^2 / 101^2 - 99^2 = ?

At first glance I thought I would factor 100 out of the top and 10 out of the bottom but that didn't work.
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Re: GMATPrep factoring question

by jayhawk2001 » Sun May 06, 2007 5:40 pm
allenkt wrote:This one has me stumped. I know the answer should be 10 but I just can't seem to figure it out. Someone please show me how to solve this one!

1001^2 - 999^2 / 101^2 - 99^2 = ?

At first glance I thought I would factor 100 out of the top and 10 out of the bottom but that didn't work.
Use a^2 - b^2 = (a+b)(a-b)

(1001+999)(1001-999) / (101+99)(101-99)
= 2000 * 2 / (200*2)
= 10
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by allenkt » Sun May 06, 2007 5:44 pm
Thanks! I knew there was an easy way but I just couldn't see it. I was trying so hard to factor that I didn't even think of doing it that way.
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