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Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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by jangelo1989 » Wed Jan 14, 2015 9:08 pm
This is probably simple but I'm just missing something...the solution to an MGMAT question states the following:


"
6/1 * 9/28 * 7/9 * 1/2 =

6/8 = 3/4

Notice that if you avoid computation until the very end, some of the numerators and denominators cancel each other out."


How did they avoid the computation? What numerators and denominators canceled out? Clearly I'm missing something and doing time costly math.
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Source: — Quantitative Reasoning |

by Brent@GMATPrepNow » Wed Jan 14, 2015 9:19 pm
Let's simplify in parts

(6/1)(9/28)(7/9)(1/2)
(6/1)(9/28)(7/9)(1/2) = (6/1)(1/28)(7/1)(1/2) [9's cancel out]

(6/1)(1/28)(7/1)(1/2)
(6/1)(1/28)(7/1)(1/2) = (6/1)(1/4)(1/1)(1/2) [7/28 simplifies to 1/4]

(6/1)(1/4)(1/1)(1/2) = 6/8 [multiply numerators and denominators]
= 3/4 [simplify]

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by jangelo1989 » Thu Jan 15, 2015 6:15 pm
Thanks, not sure how I missed that!
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