Four staff members at a certain company worked on a project.

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Four staff members at a certain company worked on a project. [#permalink]

08 Oct 2012, 01:47

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The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions Project

Four staff members at a certain company worked on a project. The amounts of time that the four staff members worked on the project were in the ratio 2 to 3 to 5 to 6. If one of the four staff members worked on the project for 30 hours, which of the following CANNOT be the total number of hours that the four staff members worked on the project?

(A) 80
(B) 96
(C) 160
(D) 192
(E) 240

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Re: Four staff members at a certain company worked on a project. [#permalink]

08 Oct 2012, 01:48

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SOLUTION

Four staff members at a certain company worked on a project. The amounts of time that the four staff members worked on the project were in the ratio 2 to 3 to 5 to 6. If one of the four staff members worked on the project for 30 hours, which of the following CANNOT be the total number of hours that the four staff members worked on the project?

(A) 80
(B) 96
(C) 160
(D) 192
(E) 240

A:B:C:D=2x:3x:5x:6x, for some positive number x. Total time 2x+3x+5x+6x=16x.

If 2x = 30 then 16x = 240;
If 3x = 30 then 16x = 160;
If 5x = 30 then 16x = 96;
If 6x = 30 then 16x = 80;

Only answer choices which is not obtained is 192.

Answer: D.
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Re: Four staff members at a certain company worked on a project. [#permalink]

08 Oct 2012, 02:59

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Let the time taken is 2x, 3x , 5x & 6x
Total time taken 16x
Any one of 2x, 3x , 5x & 6x equals 30 .
So 16x can take any of the below mentioned values -
30*16/2 , 30*16/3, 30*16/5 , 30*16/6
240 , 160, 96, 80
Answer D
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Re: Four staff members at a certain company worked on a project. [#permalink]

08 Oct 2012, 03:31

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Let the time taken as 2x, 3x , 5x & 6x
Total time taken 16x
Any one of 2x, 3x , 5x & 6x equals 30 and x can be 15, 10, 6 and 5 respectively.
Now for all values of X (15,10,6 & 5) 16x will be
= 16*15 = 240 (E)
= 16*10 = 160 (C)
= 16*6 = 96 (B)
= 16*5 =80 (A)

Hence Answer D
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Re: Four staff members at a certain company worked on a project. [#permalink]

08 Oct 2012, 10:19

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Ohh 13 the edition question luk little trickier than 12th...i didnt buy 13th yet..

well.. +1 to all above me

very nice question bunuel ..

2x, 3x, 5x, 6x...sum=16x

we r taking X as total no of hours..

2/16x=30 ...x=240

3/16x=30=then x can be =160

5/16x= 30 ...then x can be =96

6/16x= 30..then x can be =80..

D is the only choice which can not X value..

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Re: Four staff members at a certain company worked on a project. [#permalink]

09 Oct 2012, 21:57

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Four members worked in ration 2:3:5:6, hence as everyone mentioned, individual work could be taken as 2x, 3x,5x, and 6x. Also this gives us total work as 16x.
But we are told that one of these individual works is 30hrs. hence, possible scenarios, if
(1)2x =30 => 16x = 240 (2) 3x =30 => 16x = 160 (3) 5x =30 => 16x = 96 (4) 6x =30 => 16x = 80
Hence Answer is D 192 which can not be any of these.
Another alternate is to backsolve,
for options A to E, Answer/16 should give us a multiplication factor (which is denoted by x in first solution). Since this multiplication factor should be present for individual work also, 30 should be divisible by this to give individual work ratio of any out of 2,3,5,6.
eg. 80/16 =5 and 30/5 =6 or 240/16=15 and 30/15=2, but 192/16=12 and 30/12 =2.5 (not one of the ratios)
This leaves us with choice D again.

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Re: Four staff members at a certain company worked on a project. [#permalink]

11 Oct 2012, 13:15

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Re: Four staff members at a certain company worked on a project. [#permalink]

11 Oct 2012, 14:41

Hi Bunuel,

If we change this question to say that the ratios are still the same i.e 2, 3, 5 and 6 but the prompt says that the the sum of the hours worked by two of the workers is 121 and then we are asked to find the sum of total hours worked by all the workers. Would this be still a valid variation provided we restrict the number of hours in integers only?

Thanks in advance.

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Re: Four staff members at a certain company worked on a project. [#permalink]

11 Oct 2012, 14:51

aliassad wrote:

Yes.

Given: A:B:C:D=2x:3x:5x:6x, for some positive integer x and the sum of the hours worked by two of the workers is 121.

Since the only sum which gives integer value for x is 5x+6x=121 --> x=11, then total time is 16x=16*11.

Hope it helps.
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Re: Four staff members at a certain company worked on a project. [#permalink]

12 Oct 2012, 01:23

Given Ratios- 2:3:5:6
2x+3x+4x+5x=16x
lets check one by one with ACs, and when we come to D;
16x=192
=>x=12
if you put x= 12 in any individual's value (2x,3x,5x,6x) 30 can not be acheived.

Answer : D
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Re: Four staff members at a certain company worked on a project. [#permalink] 12 Oct 2012, 01:23

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