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If a continuous cable 10m long was marked off at intervals

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by Gmat_mission » Mon Apr 23, 2018 12:52 am

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If a continuous cable 10m long was marked off at intervals of 1/4 meter and also 1/5 meter, and then if the cable were cut at each mark, how many different size length of cable would result?

A. 1
B. 6
C. 4
D. 5
E. 2

[spoiler]OA=C.[/spoiler]

What is the best approach to solving this PS question? May someone helps me? Please.
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Source: — Problem Solving |

by GMATGuruNY » Mon Apr 23, 2018 2:14 am
Gmat_mission wrote:If a continuous cable 10m long was marked off at intervals of 1/4 meter and also 1/5 meter, and then if the cable were cut at each mark, how many different size length of cable would result?

A. 1
B. 6
C. 4
D. 5
E. 2
The length of the cable can be ANY VALUE.
To make the math easier, let the length of the cable = the product of the two denominators = 4*5 = 20 meters.

When the cable is divided into 4ths, markings are yielded at 5, 10, and 15:
0.................5.................10.................15.................20

When the cable is divided into 5th, markings are yielded at 4, 8, 12, and 16:
0.............4.............8.............12.............16.............20

The resulting cable looks as follows:
0............4..5........8.......10..12.........15..16..........20

When the cable is cut at each marking, the following distinct lengths are yielded:
4 meters (0 to 4 and 16 to 20)
1 meter (4 to 5 and 15 to 16)
3 meters (5 to 8 and 12 to 15)
2 meters (8 to 10 and 10 to 12)

The correct answer is C.
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by Scott@TargetTestPrep » Tue Apr 24, 2018 10:44 am
Gmat_mission wrote:If a continuous cable 10m long was marked off at intervals of 1/4 meter and also 1/5 meter, and then if the cable were cut at each mark, how many different size length of cable would result?

A. 1
B. 6
C. 4
D. 5
E. 2

Let's get a common denominator of 20.

For the intervals of 1/4 meter we have:

5/20, 10/20, 15/20 and 20/20

For the intervals of 1/5 meter we have:

4/20, 8/20, 12/20, 16/20, and 20/20

Thus, we see we could have lengths of:

5/20 - 4/20 = 1/20,

8/20 - 5/20 = 3/20,

10/20 - 8/20 = 2/20, and

20/20 - 16/20 = 4/20.

Thus we have 4 different size lengths.

Answer: C

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