


36.
Two workers A and B working together completed a job in 5 days. If A worked twice as efficiently as he actually did and B worked 1/3 as efficiently as he actually did, the work would have been completed in 3 days. A alone could complete the work in:
37.
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: [S.S.C. 2000]
38.
A can finish a work in 18 days and B can do the same work in 15 days. B worked for 10 days and left job. In how many days, A alone can finish the remaining work? [Bank P.O. 2002]
39.
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: [S.S.C. 2004]
Answer & Solution
Answer: c) 12 days
Solution: (A + B)'s 1 day's work = (1/15 + 1/10) = 1/6 Work done by A and B in 2 days = [(1/6) * 2] = 1/3. Remaining work = [1  (1/3)] = 2/3 Now 1/15 work is done by A in 1 day. 2/3 work will be done by A in[15 * (2/3)] = 10 days. Hence total time taken = 10 + 2 = 12 days. 40.
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: [S.S.C 2003]
41.
A machine P can print one lakh books in 8 hours, machine Q can print the same number of books in 10 hours while machine R can print them in 12 hours. All the machines are started at 9 a.m. while machine P is closed at 11 a.m. and the remaining two machines complete the work. Approximately at what time will the work be finished? [Bank P.O. 2003]
Answer & Solution
Answer: d) 1 p.m.
Solution: (P + Q + R)'s 1 hour's work = [1/8 + 1/10 + 1/12] = 37/120 Work done by P, Q and R in 2 hours = [(37/120) * 2] = 37/60 Remaining work = [1  (37/60)] = 23/60. (Q + R)'s 1 hour's work = [1/10 + 1/12] = 11/60. Now, 11/60 work is done by Q and R in 1 hour. So, 23/60 work will be done by Q and R in[(60/11) * (23/60)] = 23/11 hours = 2 hours. So, the work will be finished approximately 2 hours after 11 a.m., i.e. around 1 p.m. 42.
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? [C.B.I. 2003]
Answer & Solution
Answer: d) 18 days
Solution: 2 (A + B + C)'s 1 day's work = [1/30 + 1/24 + 1/20] = 15/120 = 1/8 => (A + B + C)'s 1 day's work = 1/16. Work done by A, B abd C in 10 days = 10/16 = 5/8 Remaining work = [1  (5/8)] = 3/8 A's 1 day's work = [(1/16)  (1/24)] = 1/48 Now, 1/48 work is done by A in 1 day. So, 3/8 work will be done by A in [48 * (3/8)] = 18 days 