1. A can do a piece of work in 24 days. A and B together can complete the same work in 14.4 days. In what time does B alone complete that work?
Sol: A and B together's one day's work = 1/14.4
A's one day's work = 1/24
B's one day's work = 1/14.4 - 1/24 = 1/36
B can complete the work in 36 days.
Shortcut: When two persons together can complete a work in 'x' days and one of the persons can complete in 'y' days, then the other person can complete that work in
= 36 days
2. Two pipes A and B can fill a tank in 30 minutes and 15 minutes respectively. A drain pipe C can empty a full tank in 10 minutes. In what time can the tank be filled when all the three are open simultaneously?
Sol: A = 12 minutes (+), B =15 minutes (+), C = 10 minutes (−)
All three together can fill the tank in
3. A and B can complete a piece of work in 24 days. B and C can complete it in 30 days and A and C in 40 days. In what time A, B and C together can complete that work?
4. A can do a piece of work in 30 days. He worked for 6 days and then he was joined by B and the remaining work was completed by them in 12 days. In how many days can B alone do the whole work?
5. 16 men can do a piece of work in 16 days. 4 days after they started the work, 8 more men joined them. In how many days will they take to complete the remaining work?
Shortcut: Total mandays required for the work
= 16 × 16 = 256
Number of mandays completed in 4 days
= 4 × 16 = 64
Remaining mandays = 256 − 64 = 192
Number of men available now = 16 + 8 = 24
Number of days required = 192/24 = 8
6. 25 men to complete a work in 20 days. But after 15 days only 60% work has been finished. In order to finish the work in the stipulated time, how many more men are required?
7. Ganesh can complete a piece of work in 18 days while Ganesh and Laxman together can do the same work in 12 days. In how many days will Laxman alone can do that work?
8. A tap can fill a tank in 25 minutes and another can empty it in 50 minutes. If both are opened simultaneously, in what time the tank is filled?
Ans: 50 min
9. 26 men can do a piece of work in 12 days. In how many days can 39 men do that work?
Ans: 8 days
26 × 12 = 39 × ?
? = 8
10. A can do a work in 20 days. He worked alone for 10 days and the remaining work was completed with the help of B in 2 days. In how many days will the total work be completed if they work together?
Ans: 4 days
11. A is 150% as good work man as B. If A can complete a work in 20 days, in what time both A and B together can complete that work?
Ans: 12 days
12. A can fill a tank in 4 minutes and B can fill it in 6 minutes. If both are opened alternatively for one minute each starting with A, find in what time the tank is filled.
13. A and B can complete a piece of work in 15 days and 12 days respectively. They started working together and received an amount of Rs.5400. Find the share of B.