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OG2016 - fractions

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by Brent@GMATPrepNow » Sun May 01, 2016 9:45 am
boomgoesthegmat wrote:1/(1+1/3) - 1/ (1+1/2) =

A) -1/3
B) -1/6
C) -1/12
D) 1/12
E) 1/3
USEFUL/IMPORTANT rule: 1/(a/b) = b/a
So, 1/(3/2) = 2/3
And 1/(5/6) = 6/5
etc...

Now onto the question....
1/(1 + 1/3) - 1/ (1+1/2) = 1/(4/3) - 1/ (3/2)
= 3/4 - 2/3
= 9/12 - 8/12
= 1/12
= D

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by OptimusPrep » Mon May 02, 2016 7:28 pm
boomgoesthegmat wrote:1/(1+1/3) - 1/ (1+1/2) =

A) -1/3
B) -1/6
C) -1/12
D) 1/12
E) 1/3

OA: D
Such questions might look intimidating at first, but if we solve one fraction at a time, we can easily solve them

1/(1+1/3) - 1/ (1+1/2) = 1/(4/3) - 1/(3/2) = 3/4 - 2/3 = (9-8)/12 = 1/12

Correct option: D
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by Scott@TargetTestPrep » Tue Mar 27, 2018 10:43 am
boomgoesthegmat wrote:1/(1+1/3) - 1/ (1+1/2) =

A) -1/3
B) -1/6
C) -1/12
D) 1/12
E) 1/3
The first term can be simplified as: 1/(1 + 1/3) = 1/(4/3) = 3/4

The second term can be simplified as: 1/(1 + 1/2) = 1/(3/2) = 2/3

Thus, 3/4 - 2/3 = 9/12 - 8/12 = 1/12.

Answer: D

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by [email protected] » Sat Jun 09, 2018 5:48 pm
Hi All,

We're asked for the value 1/(1+1/3) - 1/ (1+1/2). Most Test Takers would use standard Arithmetic to answer this question (which is fine). By 'converting' the fractions though, you can get the solution with a little logic and not that much math...

1/(1+1/3) = 1/1.333
1/ (1+1/2) = 1/1.5

The first fraction is BIGGER than the second fraction (because it has the smaller denominator). Since we're subtracting a smaller fraction from a larger fraction, we're looking for an answer that is POSITIVE. Since those fractions are fairly close to one another, the answer won't be that much bigger than 0. There's only one answer that matches.

Final Answer: D

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