16.  A is 30% more efficient than B. How much time will they, working together, take to complete a job which A alone could have done in 23 days?


13 days
11 days
20 3/17 days
none of these


Answer

 Option

Ratio of times taken by A and B =100 : 130 = 10 : 13. Suppose B takes x days to do the work. Then, 10 : 13 : : 23 : x = x = (23*13/10) = x = 299/10. A's 1 day's work = 1/23 ; B's 1 days work = 10/299. (A+B)'s 1 day's work = (1/23 + 10/299) = 23/299 = 1/13. therefore A and B together can complete the job in 13 days.

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17.  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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18.  A and B can do a job together in 7 days. A is 1 3/4 times as efficient as B. the same job can be done by A alone in


9 1/3 days
12 1/4 days
16 1/3 days
11 days


Answer

 Option

(A's 1 day's work) : (B's 1 day's work) = 7/4: 1 = 7:4. Let A's and B's 1 day's work be 7 x and 4x respectively. Then, 7x +4x = 1/7 = 11x= 1/7 = x = 1/77. therefore A's 1 day's work = (1/77*7) = 1/11.

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19.  A is thrice as good a workman as B and therefore is able to finish a job in 60 days less than B. working together, they can do it in


22 1/2 days
20 days
25 days
30 days


Answer

 Option

Ratio of times taken by A and B = 1:3. If different of time is 2 days, B takes 3 days. If difference of time is 60 days, B takes (3/2*60) = 90 days. so, A takes 30 days to do the work. A's 1 day's work = 1/30, B's 1 day's work =1/90. (A+B)'s 1 day's work = (1/30+ 1/90) = 4/90 = 2/45. therefore A and B together can do the work in 45/2 = 22 1/2 days.

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20.  A is twice as good a workman as B and together they finish a piece of work in 14 days. The number of days taken by A alone to finish the work is


11
28
42
21


Answer

 Option

(A's 1 day's work) : (B's 1 day's work) = 2:1. (A+B)'s 1 day's work = 1/14. Divide 1/14 in the ratio 2:1. therefore A's 1 day's work = (1/14*2/3) = 1/21. Hence, A alone can finish the work in 21 days.

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