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Re: A contractor undertakes to do a job within 20 days and hires 60 [#permalink]
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Turkish wrote:
What am I doing wrong

60 men *20 days= Total number of work 1200
Now after 5 days the amount of work that should be done was 5*60=300 but one fifth of the work was done ie 1200*1/5= 240
which means he still has= 960 amount of work
Let X be the number of men, So (60+x)15=960.. which is 4.


You are missing that initial estimation of contractor was wrong.

60 people were able to complete only 1/5 of work in 5 days. So For person, it is 1500 days work not 1200.

Hope it helps.

Sent from my SM-G955F using GMAT Club Forum mobile app
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A contractor undertakes to do a job within 20 days and hires 60 [#permalink]
Turkish wrote:
A contractor undertakes to do a job within 20 days and hires 60 people to do it. After 5 days, he realizes that one fifth of the work is done so he hires more people. How many more man he has to hire to complete the job in time?

1. 10
2. 12
3. 15
4. 20
5. 25


let 1/x=rate of one man for one day
60*1/x*5 days=1/5 of work
x=1500 days
let y=total men needed to finish job on time
y*1/1500*15 days=4/5 of work
y=80 men
80-60=20 more men needed
D
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Re: A contractor undertakes to do a job within 20 days and hires 60 [#permalink]
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Kudos
A contractor undertakes to do a job within 20 days and hires 60 people to do it. After 5 days, he realizes that one fifth of the work is done so he hires more people. How many more man he has to hire to complete the job in time?


By using the Unitary method
60 people, in 5 days can complete 1/5 part of the work
60 people, in 1 day can complete (1/5) /5 part of the work
=1/25 part of the work

Work left = 1 - 1/5
= 4/5 part
Again,
1/25 part of the work is completed in 1 day by 60 people
1 part of the work is completed in 1 day by 60 / (1/25) people
4/5 part of the work is completed in 15 days by (60 * 25 * 4)/(15*5)
= 80 people
People required = 80 – 60
= 20 people
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Re: A contractor undertakes to do a job within 20 days and hires 60 [#permalink]
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Re: A contractor undertakes to do a job within 20 days and hires 60 [#permalink]
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