27.  A can finish a work in 24 days, B in 9 days and C in 12 days. B and C start the work but are forced to leave after 3 days. The remaining work was done by A in:  
Answer: Option C Explanation:

28.  X can do a piece of work in 40 days. He works at it for 8 days and then Y finished it in 16 days. How long will they together take to complete the work?  
Answer: Option A Explanation:

29.  A and B can do a job together in 7 days. A is 1 times as efficient as B. The same job can be done by A alone in :  
Answer: Option B Explanation:
Let A’s and B’s 1 day’s work be 7x and 4x respectively.

30.  A and B together can do a piece of work in 30 days. A having worked for 16 days, B finishes the remaining work alone in 44 days. In how many days shall B finish the whole work alone?  
Answer: Option C Explanation:
Let A’s 1 day’s work = x and B’s 1 day’s work = y.
Hence, B alone shall finish the whole work in 60 days. 