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Contractor X employs 200 men to build a dam. They finish 5/6 of the wo

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Contractor X employs 200 men to build a dam. They finish 5/6 of the wo  [#permalink]

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New post 24 Nov 2019, 20:09
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Contractor X employs 200 men to build a dam. They finish 5/6 of the work in 10 months. Then rain sets in and not only does the work remain suspended for 4 months but also half of the work already done is washed away. After the rain, when the work is resumed, only 140 men turn up. The total time in which the contractor is able to complete the work assuming that there are no further disruptions in the schedule is
(a) 25 months
(b) 26 months
(c) 24 months
(d) 20 months
(e) None of these

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Re: Contractor X employs 200 men to build a dam. They finish 5/6 of the wo  [#permalink]

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New post 24 Nov 2019, 21:19
gmatbusters wrote:
Contractor X employs 200 men to build a dam. They finish 5/6 of the work in 10 months. Then rain sets in and not only does the work remain suspended for 4 months but also half of the work already done is washed away. After the rain, when the work is resumed, only 140 men turn up. The total time in which the contractor is able to complete the work assuming that there are no further disruptions in the schedule is
(a) 25 months
(b) 26 months
(c) 24 months
(d) 20 months
(e) None of these

GMATbuster's Collection


If 5/6th of work is completed in 10 months, the entire work can be completed in 10*6/5=12 months.
Now half of the work of work of 10/2 months is washed off, so remaining work is 11-5=7 months.
If 200 person can do in 7 months, 140 will do it in 200*7/140=10 months.

Total time taken including 4 months disruption =10+4+10=24 months

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Re: Contractor X employs 200 men to build a dam. They finish 5/6 of the wo  [#permalink]

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New post 24 Nov 2019, 21:57
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gmatbusters wrote:
Contractor X employs 200 men to build a dam. They finish 5/6 of the work in 10 months. Then rain sets in and not only does the work remain suspended for 4 months but also half of the work already done is washed away. After the rain, when the work is resumed, only 140 men turn up. The total time in which the contractor is able to complete the work assuming that there are no further disruptions in the schedule is
(a) 25 months
(b) 26 months
(c) 24 months
(d) 20 months
(e) None of these

GMATbuster's Collection

R(RATE)* TIME=WORK
if rate is same for workers then
X*R*t=W
200*R*10=5/6
R=1/200*2*6
Since half of the work is washed away so work done by those 200 people will be= 5/12
remaining work=1-5/12=7/12
Now 140 men with same rate
140*(1/200*2*6)*t=7/12
t=10 months
Total time= 10+4+10
=24months
C:)
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Re: Contractor X employs 200 men to build a dam. They finish 5/6 of the wo  [#permalink]

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New post 01 Dec 2019, 23:34
satya2029 wrote:
gmatbusters wrote:
Contractor X employs 200 men to build a dam. They finish 5/6 of the work in 10 months. Then rain sets in and not only does the work remain suspended for 4 months but also half of the work already done is washed away. After the rain, when the work is resumed, only 140 men turn up. The total time in which the contractor is able to complete the work assuming that there are no further disruptions in the schedule is
(a) 25 months
(b) 26 months
(c) 24 months
(d) 20 months
(e) None of these

GMATbuster's Collection

R(RATE)* TIME=WORK
if rate is same for workers then
X*R*t=W
200*R*10=5/6
R=1/200*2*6
Since half of the work is washed away so work done by those 200 people will be= 5/12
remaining work=1-5/12=7/12
Now 140 men with same rate
140*(1/200*2*6)*t=7/12
t=10 months
Total time= 10+4+10
=24months
C:)

Can you please explain how this lands to 10?

140*(1/200*2*6)*t=7/12
t=10 months
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Re: Contractor X employs 200 men to build a dam. They finish 5/6 of the wo  [#permalink]

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New post 01 Dec 2019, 23:40
PinakiRDas wrote:
satya2029 wrote:
gmatbusters wrote:
Contractor X employs 200 men to build a dam. They finish 5/6 of the work in 10 months. Then rain sets in and not only does the work remain suspended for 4 months but also half of the work already done is washed away. After the rain, when the work is resumed, only 140 men turn up. The total time in which the contractor is able to complete the work assuming that there are no further disruptions in the schedule is
(a) 25 months
(b) 26 months
(c) 24 months
(d) 20 months
(e) None of these

GMATbuster's Collection

R(RATE)* TIME=WORK
if rate is same for workers then
X*R*t=W
200*R*10=5/6
R=1/200*2*6
Since half of the work is washed away so work done by those 200 people will be= 5/12
remaining work=1-5/12=7/12
Now 140 men with same rate
140*(1/200*2*6)*t=7/12
t=10 months
Total time= 10+4+10
=24months
C:)

Can you please explain how this lands to 10?

140*(1/200*2*6)*t=7/12
t=10 months

Rate* time= work
Since rate is same for all the 140 men
140* Rate* time= work

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Re: Contractor X employs 200 men to build a dam. They finish 5/6 of the wo  [#permalink]

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New post 02 Dec 2019, 00:34
gmatbusters wrote:
Contractor X employs 200 men to build a dam. They finish 5/6 of the work in 10 months. Then rain sets in and not only does the work remain suspended for 4 months but also half of the work already done is washed away. After the rain, when the work is resumed, only 140 men turn up. The total time in which the contractor is able to complete the work assuming that there are no further disruptions in the schedule is
(a) 25 months
(b) 26 months
(c) 24 months
(d) 20 months
(e) None of these

GMATbuster's Collection



    • 200 men can complete \(\frac{5}{6}^{th}\) work in 10 months
    • 200 men can complete 1 work in \(\frac{10}{(5/6)}\) months = \(6*\frac{10}{5} = 12\) months
      o Ideally only 12 – 10 = 2 months of work should have been left.
However, half of the work done by them so far got wasted. They worked for 10 months and if half of it is wasted then that means 5 months of work is wasted.
    • So, now the 200 men need to complete = 5 month of rework + 2 months of work left = 7 months of work.
However, we have only 140 men, so we’ll need to more time.
    • 200 men complete the work in 7 months
    • 1 man can complete it in 7*200 months
    • 140 men can complete the work in \((7*\frac{200}{140}) = 10\) months.
Thus, total time taken to complete the project = 10 months + 4 months of delay + 10 months = 24 months.

Correct Answer: Option C
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Re: Contractor X employs 200 men to build a dam. They finish 5/6 of the wo   [#permalink] 02 Dec 2019, 00:34
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