Work & Time

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Work & Time

by neya » Mon Aug 01, 2011 7:16 pm
12 Children take 16 days to complete a work which can be completed by 8 adults in 12days. 16 Adults started working for 3 day,10 adults left & 4children joined them. How many days will it take them to complete the remaining work?
1.6
2.8
3.A
4.3
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by Anurag@Gurome » Mon Aug 01, 2011 7:54 pm
neya wrote:12 Children take 16 days to complete a work which can be completed by 8 adults in 12days. 16 Adults started working for 3 day,10 adults left & 4children joined them. How many days will it take them to complete the remaining work?
1.6
2.8
3.A
4.3
1 day work of 1 child = 1/(12*16) = 1/192
1 day work of 1 adult = 1/(12*8) = 1/96
3 days work of 16 adults = (3*16) * 1/96 = 1/2
Remaining work = 1 - 1/2 = 1/2
1 day work 6 adults + 4 children = 6/96 + 4/192 = 1/12
1/12 work is done in 1 day
So, 1/2 work will be done in (1/2)*12 = 6 days

The correct answer is 1.
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by GMATGuruNY » Mon Aug 01, 2011 9:21 pm
neya wrote:12 Children take 16 days to complete a work which can be completed by 8 adults in 12days. 16 Adults started working for 3 day,10 adults left & 4children joined them. How many days will it take them to complete the remaining work?
1.6
2.8
3.A
4.3
Let rate per adult = 2 units per day.
Number of units produced by 8 adults each day = 8*2 = 16 units.
Over 12 days, number of units produced = 12*16 = 192 units. This is the value of the job.

Since the children take 16 days, number of units produced by the 12 children each day = 192/16 = 12.
Since the 12 children produce 12 units each day, rate for each child = 1 unit per day.

Rate for 16 adults = 16*2 = 32 units per day.
In 3 days, number of units produced = 3*32 = 96.
Remaining work = 192 - 96 = 96 units.

Rate for 10 remaining adults and 4 children = 10*2 + 4*1 = 16 units per day.
Time to finish the remaining 96 units = 96/16 = 6 days.

The correct answer is A.
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