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?

A. 13 days B. 11 days C. 20 3/17 days D. none of these

Answer Answer: Option A Explanation: 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.

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

A. 15 B. 16 C. 18 D. 25

Answer Answer: Option B Explanation: 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

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

A. 22 1/2 days B. 20 days C. 25 days D. 30 days

Answer Answer: Option A Explanation: 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.

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

A. 11 B. 28 C. 42 D. 21

Answer Answer: Option D Explanation: (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.