X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last ?

A. 6 days
B. 10 days
C. 15 days
D. 20 days

Work done by X in 4 days = ( 1/20X 4 ) = 1/5 Remaining work = (1 – 1/5 ) = 4/5 (X + Y)’s 1 day’s work = 1/20 + 1/12 = 8/60 = 2/15 Now, 2/15 work is done by X and Y in 1 day. So, 4/5 work will be done by X and Y in 15/2 X 4/5 = 6 days Hence, total time taken = (6 + 4) days = 10 days.

Related Mcqs:

P and Q can complete a work in 20 days and 12 days respectively. P alone started the work and Q joined him after 4 days till the completion of the work. How long did the work last?
A. 5 days
B. 10 days
C. 15 days
D. 12 days
A and B can complete a work in 15 days and 10 days respectively. They started doing the work together but after 2 days B had to leave and A alone completed the remaining work. The whole work was completed in___________?
A. 8 days
B. 10 days
C. 12 days
D. 15 days
P and Q can complete a work in 15 days and 10 days respectively. They started the work together and then Q left after 2 days. P alone completed the remaining work. The work was finished in__________days.
A. 12
B. 15
C. 22
D. 20
P and Q can do a work in 30 days. Q and R can do the same work in 24 days and R and P in 20 days. They started the work together, but Q and R left after 10 days. How many days more will P take to finish the work?
A. 10
B. 8
C. 18
D. 19
A and B can finish a work 30 days if they work together. They worked together for 20 days and then B left. A finished the remaining work in another 20 days. In how many days A alone can finish the work?
A. 70
B. 50
C. 40
D. 60
A and B can together do a piece of work in 15 days. B alone can do it in 20 days. In how many days can A alone do it ?
A. 40 days
B. 50 days
C. 60 days
D. 70 days
A alone can finish a work in X days. B alone can finish the same work in X+5 days. Together, they take 6 days to complete the work. Find X
A. 12
B. 8
C. 10
D. 9
P can do a work in the same time in which Q and R together can do it. If P and Q work together, the work can be completed in 10 days. R alone needs 50 days to complete the same work. then Q alone can do it in__________?
A. 30 days
B. 25 days
C. 20 days
D. 15 days
A and B can do a piece of work in 21 and 24 days respectively.They start the work together and after some days, A leaves and B completes the rest of the task in 9 days. After how many days did A leave?
A. 5
B. 6
C. 7
D. 8
A and B can finish a piece of work in 20 days .B and C in 30 days and C and A in 40 days. In how many days will A alone finish the job?
A. 48
B. 34(2/7)
C. 44
D. 45