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work and work

by maihuna » Mon May 04, 2009 10:38 am
A contractor undertook to do a certain piece of work in 9 days. He employed certain number of men , but 6 of them being absent from the very first day, the rest could finish the work in 15 days. The no of men originally employed were:
3
4
5
6
9

A contractor employed 30 men to do a piece of work in 38 days, after 25 days he employed 5 men more and the work was finished one day earlier. how many days he would have been behind if he had not employed additional men:

1
5/4
3/2
7/4
2
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by PussInBoots » Mon May 04, 2009 12:03 pm
Are these trick questions?
#1: no of men originally employed has to be > 6 otherwise if 6 workers were absent from the very first day, project would not have been completed
But answer 9 is not correct either.

#2: I cannot even tackle this one. How could a contractor be behind a deadline more than 1 day if after hiring additional workers, the project was done 1 day earlier.
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Re: work and work

by Brent@GMATPrepNow » Mon May 04, 2009 4:12 pm
maihuna wrote:A contractor undertook to do a certain piece of work in 9 days. He employed certain number of men , but 6 of them being absent from the very first day, the rest could finish the work in 15 days. The no of men originally employed were:
3
4
5
6
9

A contractor employed 30 men to do a piece of work in 38 days, after 25 days he employed 5 men more and the work was finished one day earlier. how many days he would have been behind if he had not employed additional men:

1
5/4
3/2
7/4
2
For both questions, we need to employ the notion of "man days." For example, if it takes 7 men working 9 days each to complete a job, then the job takes 63 "man days" (7x9) to complete. So, we can also conclude that if there were only 3 men working on the job, then the same job would take 21 days (63/3) to complete.

Question 1:
Let x be the number of men originally hired.
Since it is not explicitly stated in the question, we must assume that these x men would have completed the job in 9 days (given the ambiguity, I'm pretty sure this is not an official question :-). So, the job will take 9x man days to complete.

If 6 men do not come to work, then there are x-6 men and it takes them 15 days to complete the same job. In other words, the number of man days required is 15(x-6)

We can create the equation 9x = 15(x-6)
When we solve for x, we get x=15.
So, there must have been 15 men originally. (The answer is not provided in the choices)

Question 2:
Determine the total number of man days required to complete the job.
30 men working for 25 days = 750 man days (30x25)
35 men working for 12 days = 420 man days (35x12)
Total number of man days to complete the job = 1170

If the contractor had not hired the additional men it would have taken 1170/30 days for the thirty men to complete the job.

1170/30 = 39, so it would have taken one extra day to complete the job. The answer is A
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by maihuna » Tue May 05, 2009 4:38 am
Hi bren,
here we go(where is dumb btw):

A contractor undertook to do a certain piece of work in 9 days. He employed certain number of men , but 6 of them being absent from the very first day, the rest could finish the work in 15 days. The no of men originally employed were:
=========================
Let n = no of men

so 9n = (n-6)*15
so 9n = 15n -90 or 6n = 90 or n=15
Since 6 are abscent work started wit 15-6 = 9 mens.
===========================


A contractor employed 30 men to do a piece of work in 38 days, after 25 days he employed 5 men more and the work was finished one day earlier. how many days he would have been behind if he had not employed additional men:
============================
originally thought : 30*38 = 1140
now: 30*25 + (30+5)*(38-25-1) = 750+35*12 = 750+420 = 1170

so adiitional work = 1170-1140 so yes 30 so yes 1 day for 30 men
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by Brent@GMATPrepNow » Tue May 05, 2009 5:25 am
A contractor undertook to do a certain piece of work in 9 days. He employed certain number of men , but 6 of them being absent from the very first day, the rest could finish the work in 15 days. The no of men originally employed were:
=========================
Let n = no of men

so 9n = (n-6)*15
so 9n = 15n -90 or 6n = 90 or n=15
Since 6 are abscent work started wit 15-6 = 9 mens.
Hmm, it seems that the contractor originally employed 15 men but 6 did not show up. If you want the answer to be 9, perhaps the question should read, "The number of men that showed up for work was "
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