GMATPrep2 problem- need shorter method

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jaydeer44: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Mon Feb 25, 2008 10:36 pm

by jaydeer44 » Mon Aug 25, 2008 1:31 pm

Can someone please tell me what the easiest way to solve this problem would be? The answer is A. Thanks!

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Source: Beat The GMAT — Problem Solving | Mon Aug 25, 2008 1:31 pm

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Ian Stewart: GMAT Instructor; Posts: 2623; Joined: Mon Jun 02, 2008 3:17 amFollowed by: 355 members; Location: Montreal; Thanked: 1090 times; GMAT Score:780

by Ian Stewart » Mon Aug 25, 2008 1:51 pm

The numerator and denominator are both differences of squares:

1001^2 - 999^2 = (1001+999)(1001-999) = 2000*2
101^2 - 99^2 = (101+99)(101-99) = 200*2

Cancel (2000*2)/(200*2) to get 10.

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jaydeer44: Senior | Next Rank: 100 Posts; Posts: 44; Joined: Mon Feb 25, 2008 10:36 pm

by jaydeer44 » Mon Aug 25, 2008 1:56 pm

thanks so much!

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