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Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Question

by sukh » Sat Sep 10, 2011 1:19 am
If w, x, y, and z are consecutive odd integers and
w < x < y < z, then w + x is how much less than y + z ?
(A) 2
(B) 4
(C) 8
(D) 10
(E) 16
Last edited by sukh on Sat Sep 10, 2011 1:38 am, edited 1 time in total.
Source: — Quantitative Reasoning |

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by shankar.ashwin » Sat Sep 10, 2011 1:26 am
Assume set of forst 4 cons odd numbers.

1,3,5,7.

1+3=4
5+7=12.

12-4=8

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by Brent@GMATPrepNow » Sat Sep 10, 2011 6:34 am
shankar.ashwin's solution is perfect.

That said, I'd like to mention that, with some consecutive odd integer questions, it helps to know that consecutive odd integers can be represented algebraically as k, k+2, k+4, k+6, etc (where each value is 2 greater than the one before it.

So, to solve this question, we can first make the following observations:
- w is the smallest integer.
- Since x is the next odd integer, we can say that x = w+2
- Since y is the next odd integer, we can say that y = w+4
- Since z is the next odd integer, we can say that z = w+6

The question asks, "w + x is how much less than y + z?"
In other words, [w + w+2] is how much less than [w+4 + w+6]?
When we simplify, we get [2w+2] is how much less than [2w+10]?, and we can see that the answer is 8

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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