26.

Worker A takes 8 hours to do a job. Worker B takes 10 hours to do a job. How long should it take both A and B, working together to do same job.

 A. [Math Processing Error] B. [Math Processing Error] C. [Math Processing Error] D. [Math Processing Error]
Explanation: In this type of questions, first we need to calculate 1 hours work, then their collective work as, A's 1 hour work is 1/8 B's 1 hour work is 1/10 (A+B)'s 1 hour work = 1/8 + 1/10 = 9/40 So both will finish the work in 40/9 hours = [Math Processing Error]

27.

A and B can together complete a piece of work in 4 days. If A alone can complete the same work in 12 days, in how many days can B alone complete that work ?

 A. 4 days B. 5 days C. 6 days D. 7 days
Explanation: (A+B)'s 1 day work = 1/4 A's 1 day work = 1/12 B's 1 day work = [Math Processing Error] So B alone can complete the work in 6 days

28.

A does a work in 10 days and B does the same work in 15 days. In how many days they together will do the same work ?

 A. 5 days B. 6 days C. 7 days D. 8 days
Explanation: Firstly we will find 1 day work of both A and B, then by adding we can get collective days for them, So, A's 1 day work = 1/10 B's 1 day work = 1/15 (A+B)'s 1 day work = [Math Processing Error] So together they can complete work in 6 days.

29.

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

 A. 1\5 B. 1\6 C. 1\7 D. 1\8