work & time

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work & time

by [email protected] » Thu Jul 01, 2010 7:36 pm
How many hours does it take some boys and girls in a camp to put up the tent? I. There are 4 boys and 7 girls. II. A girl can put up the tent in 5 hours and a boy can put up the tent in 3 hours.
A)l B)2 C)3 D)4

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by albatross86 » Thu Jul 01, 2010 7:44 pm
A girl can put up 1 tent in 5 hours => In 1 hour she puts up 1/5 th of the tent
Similarly a boy can put up 1/3rd of the tent in 1 hour.


=> 4 boys will put up 4/3 tents in 1 hour
=> 7 girls will put up 7/5 tents in 1 hour

In X hours, 4 boys and 3 girls together will put up the complete tent:

X*(4/3 + 7/5) = 1

=> X*(20 + 21) = 15

=> X = 15 / 41 ...Ans


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