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GMAT Prep - Exponents and Factoring

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GMAT Prep - Exponents and Factoring

by tonebeeze » Fri May 20, 2011 12:44 pm
What is the best way not to get tripped up or slowed down by these problems?

{(1000)^2 - (999)^2} / {(101)^2 - (99)^2} =

a. 10
b. 20
c. 40
d. 80
e. 100

OA = 10
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by Ian Stewart » Fri May 20, 2011 12:57 pm
If you found this question time-consuming, you'll certainly benefit from learning to recognize the difference of squares whenever it shows up - it will almost definitely appear on your real GMAT. If you ever have anything in the a^2 - b^2 pattern, you can factor it as (a+b)(a-b). So in the question above,

(1001^2 - 999^2)/(101^2 - 99^2) = [(1001+999)(1001-99))]/[(101+99)(101-99)] = (2000*2)/(200*2) = 10
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