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Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Source: — Quantitative Reasoning |
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by beat_gmat_09 » Thu Nov 25, 2010 7:15 pm
Use formula - (a^2 - b^2) = (a+b)*(a-b)
(1001^2 - 999^2)/(101^2 - 99^2)
= (1001+999) * (1001-999) / (101+99)*(101-99)
= (2000 * 2) / (200 *2)
= 10
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by haidgmat » Fri Nov 26, 2010 6:33 am
that was so easy! can't believe I didn't think of it!!

Thanks!
beat_gmat_09 wrote:Use formula - (a^2 - b^2) = (a+b)*(a-b)
(1001^2 - 999^2)/(101^2 - 99^2)
= (1001+999) * (1001-999) / (101+99)*(101-99)
= (2000 * 2) / (200 *2)
= 10
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