WORK-TIME AND UNITARY METHOD (CDS)

Total Questions: 53

21. A can do 50% more work than B in the same time. B alone can do a piece of work in 30 h. B starts working and had already worked for 12 h when A joins him. How many hours should B and A work together to complete the remaining work? [2016 (II) Evening Shift]

Correct Answer: (d) 7.2 h
Solution:We have, A can do 50% more work than B in same hour.


22. A tank can be filled by pipe X in 2 h and pipe Y in 6 h. At 10 am, pipe X was opened. At what time will the tank be filled if pipe Y is opened at 11 am? [2016 (II) Evening Shift]

Correct Answer: (c) 11:45 am
Solution:Part of tank filled by X in h = 1/2

23. Outside a meeting room, Madhukar was told by a person that each meeting takes place after 13/4 h. The last meeting has been over just 45 min ago and the next meeting will take place at 2 pm. At what time did Madhukar receive this information? [2016 (I) Morning Shift]

Correct Answer: (b) 11 : 30 am
Solution:

24. Two pipes A and B can fill a tank in 60 min and 75 min, respectively. There is also an outlet C. If A, B and C are opened together, then the tank is full in 50 min. How much time will be taken by C to empty the full tank? [2016 (I) Morning Shift]

Correct Answer: (a) 100 min
Solution:Since, two pipes A and B fill a tank in 60 min and 75 min, respectively.


25. A and B are two taps which can fill a tank individually in 10 min and 20 min, respectively. However, there is a leakage at the bottom, which can empty a filled tank in 40 min. If the tank is empty initially, then how much time will both the taps take to fill the tank with leakage? [2015 (II) Evening Shift ]

Correct Answer: (d) 8 min
Solution:We have, tap A fill the tank in 10 min.

26. If 4 men working 4 h per day for 4 days complete 4 units of work, then how many units of work will be completed by 2 men working for 2h per day in 2 days? [2015 (II) Evening Shift ]

Correct Answer: (c) 1/2
Solution:4 men working 4 h per day for 4 days complete 4 units of work i.e. 4 units of work completed in (4 × 4 × 4) h.

27. If m persons can paint a house in d days, then how many days will it take for (m + 2) persons to paint the same house? [2015 (II) Evening Shift ]

Correct Answer: (d)
Solution:m persons paint a house ind days.

28. The efficiency of P is twice that of Q, whereas the efficiency of P and Q together is three times that of R. If P Q, and R work together on a job, then in what ratio should they share their earnings? [2015 (I) Morning Shift ]

Correct Answer: (a) 2 : 1 : 1
Solution:Let P can finish the work = x days, Q can finish the work = 2x days

29. Pipe A can fill a tank in 3 h but there is a leakage also, due to which it takes 3.5 h for the tank to be filled. How much time will the leakage take in emptying the tank, if the tank is filled initially? [2014 (II) Evening Shift ]

Correct Answer: (a) 21 h
Solution:Given, pipe A can fill the tank in 3 h.

30. A B, and C can do a piece of work individually in 8, 12 and 15 days, respectively. A and B start working together but A quits after working for 2 days. After this, C joins and works till completion of the work. In how many days, will the work be completed? [2014 (II) Evening Shift ]

Correct Answer: (b) 5⁸⁄₉ days
Solution:Work done by A in one day = 1/8