Question

A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for the first half of the day daily, then in how many days will A and B together complete the work?

• A. 15 days
• B. 22/3 days
• C. 43/2 days
• D. 40/3 days

Answer 1

Answer:

A. 15 days

A and B can complete a work in = 12 days A alone can complete = 20 LCM of these two are the total work = 60 efficiency of A and B = 60/12=5 efficiency of A =60/20=3 efficiency of B = 5-3 =2 half day efficiency =2/2=1 half day of B and full day of A = 3+1=4 so the total number of days = 60/4=15 days