31.  A can do a work in 15 days and B in 20 days. if they work on it together for 4days, then the fraction of the work that is left is?


1/4
1/10
7/15
8/15


Answer

 Option

A's 1 day's work = 1/15; B's 1 day's work = 1/20. (A+B)'s 1 day's work = (1/15+ 1/20) = 7/60. (A+B)'s 4 day's work = (7/60 * 4) = 7/15. therefore Remaining work = (1- 7/15) = 8/15.

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32.  A can do a piece of work in 80 days.He works at it for 10 days and then B alone finishes the remaining work in 42 days.In how much time will A and B working together finish the work?


25 days
30 days
32 days
26 days


Answer

 Option

Work done by A in 10 days = (1/80 * 10) =1/8 Remaining work = (1- 1/8) = 7/8 Now 7/8 work is done by B in 42 days Whole work will be done by B in (42*8/7) = 48 days A's 1 day's work = 1/80 and B's 1 day's work = 1/48 (A+B)'s 1 day's work = (1/80 + 1/48) = 8/240 = 1/30 Hence both will finish the work in 30 days.

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33.  A can do a piece of work in 4 hours; B and C together can do it in 3 hours, while A and C together can do it in 2 hours. How long will B alone take to do it?


8 hours
12 hours
10 hours
24 hours


Answer

 Option

A's 1 hour's work = 1/4; (B+C)'s 1 hour's work = 1/3; (A+C)'s 1 hour's work = 1/2. (A+B+C)'s work = (1/4+1/3) = 7/12. B's 1 hour's work = (7/12 - 1/2) = 1/12. therefore B alone will take 12 hours to do the work.

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34.  A can do a piece of work in 20 days. B is 25% more efficient than A. The number of days taken by B to do the same piece of work is


15
16
18
25


Answer

 Option

Ratio of times taken by A and B = 125 : 100 = 5 :4. suppose B takes x days to do the work. 5 : 4 : : 20 : x = x = (4 *20/ 5) = x = 16 days. hence B takes 16 days to complete the work

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35.  A can do a certain work in the same time in which B and C together can do it. If A and B together could do it in 10 days and C alone in 50 days, then B alone could do it in


15 days
20 days
25 days
30 days


Answer

 Option

(A+B)'s 1 day's work = 1/10; C's 1 day's work = 1/50. (A+B+C)'s 1 day's work = (1/10+ 1/50) = 6/50 = 3/25 Also, A's 1 day's work = (B+C)'s 1 day's work From(1)and (2) we get : 2* (A's 1 day's work) = 3/25. = A's 1 day's work = 3/50. therefore B's 1 day's work = (1/10 - 3/50) = 2/50 = 1/25. so, B alone could do the work in 25 days.

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