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shanice: Master | Next Rank: 500 Posts; Posts: 110; Joined: Thu Apr 05, 2012 8:48 am; Thanked: 3 times; Followed by:1 members

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by shanice » Thu Jun 21, 2012 8:02 pm

Simplify : x-1/2 - 2x-1/3

My workings are as follows:-

3x-3/6 - 4x-2/6 = 3x-3-4x+2/6= -x-1/6

So, my answer is -x-1/6. However, the book states -x+1/6 as the answer.

Can someone help please?

Thank you.

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Source: Beat The GMAT — Problem Solving | Thu Jun 21, 2012 8:02 pm

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Thu Jun 21, 2012 9:27 pm

shanice wrote:Simplify : x-1/2 - 2x-1/3

If there is no brackets or parentheses, then this will simplify as follows...

# x - 1/2 - 2x - 1/3
= -x - 1/2 - 1/3
= -x - 3/6 - 2/6
= -x - 5/6

But if the expression is (x - 1/2) - (2x - 1/3), then the simplification will be,

# (x - 1/2) - (2x - 1/3)
= (x - 1/2 - 2x + 1/3)
= -x - 3/6 + 2/6
= -x - 1/6

shanice wrote:3x-3/6 - 4x-2/6 = 3x-3-4x+2/6= -x-1/6

You can't do that.
(x - 1/2) and (2x - 3/6) are different.
(x - 1/2) can be written as (x - 2/4) or (x - 3/6) or (x - 50/100) but you cannot simply change the coefficient of x. Coincidentally in this case the difference you got is same, but this is wrong.

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