41.  A man can do a piece of work in 5 days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone?


6 1/2 days
7 days
7 1/2 days
8 days


Answer

 Option

Son's 1 day's work = (1/3- 1/5) = 2/15. Therefore the son alone can do the work in 15/2 = 7 1/2 days.

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42.  A man can do a job in 15 days. His father takes 20 days and his son finishes it in 25 days. How long will they take to complete the job if they all work together?


Less than 6 days
Exactly 6 days
Approximately 6.4 days
More than 10 days


Answer

 Option

1 day's work of the three persons = (1/15+ 1/20+1/25) = 47/300. so, all the three together will complete the work in 300/47 = 6.4 days.

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43.  A,B and C can complete a piece of work in 24,6 and 12 days respectively. Working together, they will complete the same work in


3 3/7 days
1/24 days
7/24 days
4 days


Answer

 Option

(A+B+C)'s 1 day's work = (1/24+ 1/6+ 1/12) = 7/24. so A,B and C together will complete the job in 24/7 = 3 3/7 days.

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44.  A Tyre has two punctures. The first puncture alone would have made the Tyre flat in 9 minutes and the second alone would have done it in 6 minutes.If air leaks out at a constant rate, how long does it take both the punctures together to make it flat?


1 1/2 minutes
3 1/2 minutes
3 3/5 minutes
4 1/4 minutes


Answer

 Option

1 minute's work of both the punctures = (1/9+ 1/6) = 5/18. so, both the punctures will make the Tyre flat in 18/5 = 3 3/5min.

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45.  A can finish a work in 18 days days and B can do the same work in half the time taken by A. Then,working together, what part of the same work they can finish in a day?


1/6
1/9
2/5
2/7


Answer

 Option

A's 1 day's work = 1/18 and B's 1 day's work =1/9. therefore (A+B)'s 1 day's work = (1/18+1/9) = 1/6.

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