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 Post subject: GMAT Geometry
PostPosted: Fri Jul 16, 2010 9:52 pm 
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Joined: Sun May 30, 2010 3:15 am
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A piece of string is marked in segments of one-fourth and one-third the string's length. If the string is then cut at each mark, which of the following lists all the different lengths of the bits of string, in fractions of the original length?

A. 1/12 and 1/4 only
B. 1/4 and 1/3 only
C. 1/6, 1/4 and 1/3
D. 1/12, 1/6, and 1/4
E. 1/12, 1/6, and 1/3

(D) This is one of those word problems that you should translate into a diagram. You have a piece of string marked into fourths and thirds.

To make things easy, assume that the string is 1 foot long. Whatever the actual length, the relative lengths of the pieces will be the same. 1 foot is also convenient, as it equals 12 inches, and 12 is the least common denominator of the fractions in the problem.

Making cuts every one-fourth the length of the string means making cuts every 3 inches. A cut every third the length of the string means a cut every 4 inches. Some of the segments would then be 3 inches long, some are 2, and some are 1, or 1/4, 1/6, 1/12 of the whole.

Choice (A) is wrong because it says "only" and there are other options available.
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How do you know what order to cut the marks in? What if I choose to cut the 1/3 marks before the 1/4 marks?


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 Post subject: Re: math (test 5, question 8): logic, arithmetic
PostPosted: Fri Jul 16, 2010 10:07 pm 
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Joined: Sun May 30, 2010 2:23 am
Posts: 498
The order how you cut marks, once you've marked them, is not important. However, note that you mark string with all the marks first and then make cuts.

If you mark string only with 1/3 marks you'll get:
Image

If you mark string only with 1/4 marks you'll get:
Image

If you mark string with both: 1/3 and 1/4 marks you'll get:
Image


Attachments:
both.gif [3.13 KiB]
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1_4.gif [2.45 KiB]
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1_3.gif [2.24 KiB]
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