11.  A can lay railway track between two given stations in 16 days and B can do the same job in 12 days. With the help of C, they did the job in 4 days only. Then, C alone can do the job in


9 1/5 days
9 2/5 days
9 3/5 days
10 days


Answer

 Option

(A+B+C)'s 1 day's work = 1/4, A's 1 day's work = 1/16, B's 1 day's work = 1/12 therefore C's 1 day's work = 1/4 - ( 1/16+ 1/12) = (1/4 - 7/48) = 5/48. so, c alone can do the work in 48/5 = 9 3/5 days.

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12.  A takes twice as much time as B or thrice as much time to finish a piece of work. Working together, they can finish the work in 2 days. B can do the work alone in


4 days
6 days
8 days
12 days


Answer

 Option

Suppose A,B and C take x, x/2 and x/3 hours respectively to finish the work. Then, (1/x+ 2/x+3/x) = 1/2 = x = 12. so, B takes 6 hours to finish the work.

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13.  X can do 1/4 of a work in 10 days, Y can do 40% of the work in 40 days and Z can do 1/3 of the work in 13 days. Who will complete the work first?


X
Y
Z
X and Z both


Answer

 Option

Whole work will be done by X in (10*4) = 40 days. Whole work will be done by Y in (40*100/40) = 100 days. Whole work will be done by Z in (13*3) = 39 days. Therefore Z will complete the work first.

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14.  A is twice as good a workman as B and together they finish a piece of work in 18 days.In how many days will A alone finish the work?


24 days
22 days
27 days
21 days


Answer

 Option

(A's 1 day's work) : (B's 1 day's work) = 2:1 (A+B)'s 1 day's work = 1/18 Divide 1/18 in the ratio 2:1 A's 1 day's work = (1/18 * 2/3) = 1/27 Hence A alone can finish the work in 27 days

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15.  A can do a certain job in 12 days. B is 60% more efficient than A. How many days does B alone take to do the same job?


15/2
17/2
14/2
18/2


Answer

 Option

Ratio of times taken by A and B = 160:100 = 8:5 suppose B alone takes X days to do the job. Then 8:5::12: x = 8x = 5*12 = x = 7 1/2 days or 15/2 days

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