Important Facts and Formulae 

(1)P can complete a work in 12 days working 8 hours a day.Q can complete the same work in 8 days working 10 hours a day.If both P and Q work together,working 8 hours a day,in How many days can they complete the work?(Asked in Bank PO Exam 1999)
 60/11
 61/11
 71/11
 72/11
(2)A and B can do a work in 12 days,B and C can do the same work in 12 days.A,B and C together can finish it in 6 days.A and C together will do it in:
 5 days
 47/6 days
 10 days
 47/3 days
(3)A and B can do a work in 8 days,B and C can do the same work in 12 days.A,B and C together can finish it in 6 days.A and C together will do it in:
 4 days
 6 days
 8 days
 12 days
(4)A and B can do a piece of work in 72 days,B and C can do it in 120 days,A and C can do it in 90 days.In what time can A alone do it?
 80 days
 100 days
 120 days
 150 days
(5)A works twice as fast as B.If B can complete a work in 12 days independently,the number of days in which A and B can together finish the work is:
 4 days
 6 days
 8 days
 18 days
(6)A is thrice as good a workman as B and therefore is able to finish a job in 60 days less than B.Working together,they can do it in:
 20 days
 45/2 days
 25 days
 30 days
(7)A and B can do a job together in 7 days.A is 7/4 times as efficient as B.The same job can be done by A alone in:
 28/3
 11 days
 49/4
 49/3
(8)A can do a work in 15 days and B in 20 days.If they work on it together for 4 days,then the fraction of the work that is left is:
 1/4
 1/10
 7/15
 8/15
(9)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?(bank Po 2004)
 6 days
 10 days
 15 days
 20 days
(10)A and B can do a piece of work in 30 days,while B and C can do the same work in 24 days and C and A in 20 days.They all work together for 10 days when B and C leave.How many days more will A take to finish the work?
 18 days
 24 days
 30 days
 36 days
Answers
Question Number  Answer 
1  60/11 
2  10 days 
3  8 days 
4  120 days 
5  4 days 
6  45/2 days 
7  11 days 
8  8/15 
9  10 days 
10  18 days 