841. is able to do a piece of work in 15 days and Q can do the same work in 20 days. If they can work together for 4 days, what is the fraction of work left?
A. 8/15
B. 7/15
C. 11/15
D. 2/11

Explanation:
Amount of work P can do in 1 day = 1/15
Amount of work Q can do in 1 day = 1/20
Amount of work P and Q can do in 1 day = 1/15 + 1/20 = 7/60
Amount of work P and Q can together do in 4 days = 4 × (7/60) = 7/15
Fraction of work left = 1 – 7/15= 8/15

842. Two pipes P and Q can fill a cistern in 12 min. and 15 min. respectively but a third pipe ‘R’ can empty the full tank in 6 min. P and Q are kept open for 5 min. in the beginning and then ‘R’ is also opened. In what time is the cistern emptied ?
A. 30 min
B. 35 min
C. 40 min
D. 45 min

843. A and B can together do a piece of work in 15 days. B alone can do it in 20 days. In how many days can A alone do it ?
A. 40 days
B. 50 days
C. 60 days
D. 70 days

Explanation:
(A+B)’S 1 day’s work = [1/15−1/20]=1/60
A alone can finish it in 60 days

844. Farjan and Kashif can complete a task in 30 days. Farjan leaves after 20 days and Kashif alone completes it in another 25 days. How many days does Farjan alone take to complete the entire task?
A. 50
B. 75
C. 60
D. 45

Explanation:
Part of work completed by Farjan and Kashif in a day
= 1/30 Part of work completed by them in 20 days
= 20/30 = 2/3 1/3 of the work is remaining. Kashif completes 1/3rd of the work in 25 days. Part of work completed by him in a day
= (1/3)÷25
= 1/75 (1/D)+(1/V) = 1/30 (1/D) = (1/30)-(1/75) = 1/50 Farjan can complete it in 50 days.

845. Jameel can complete a task in 15 hours and Nasir can complete the same task in 12 hours. Jameel starts the task at 9:00 am and stops working at 2:00pm. Nasir starts working on the task at 4:00 pm. At what time is the task completed?
A. 12:00 pm
B. 2:00 am
C. 12:00 am
D. 10:00 pm

Explanation:
Jameel works for 5 hours. So he completes 5/15 = 1/3 of the task Nasir has to complete 2/3rd of the task 12*2/3 = 8 hours are needed. He completes the task at 12:00 am.

846. P can do a work in 24 days. Q can do the same work in 9 days and R can do the same in 12 days. Q and R start the work and leave after 3 days. P finishes the remaining work in_________days.
A. 10
B. 9
C. 11
D. 12

Explanation:
Work done by P in 1 day = 1/24
Work done by Q in 1 day = 1/9
Work done by R in 1 day = 1/12
Work done by Q and R in 1 day = 1/9 + 1/12 = 7/36
Work done by Q and R in 3 days = 3×7/36 = 7/12
Remaining work = 1 – 7/12 = 5/12
Number of days in which P can finish the remaining work = (5/12) / (1/24) = 10

847. Kamal will complete work in 20 days. If Suresh is 25% more efficient than Kamal, he can complete the work in________days.
A. 14
B. 16
C. 15
D. 11

Explanation:
Work done by Kamal in 1 day = 1/20
Work done by Suresh in 1 day = (1/20) × (125/100) = 5/80 = 1/16
=> Suresh can complete the work in 16 days

848. A completes 80% of a work in 20 days. Then B also joins and A and B together finish the remaining work in 3 days. How long does it need for B if he alone completes the work?
A. 37 ½ days
B. 22 days
C. 31 days
D. 22 days

Explanation:
Work done by A in 20 days = 80/100 = 8/10 = 4/5
Work done by A in 1 day = (4/5) / 20 = 4/100 = 1/25 — (1)
Work done by A and B in 3 days = 20/100 = 1/5 (Because remaining 20% is done in 3 days by A and B)
Work done by A and B in 1 day = 1/15 —(2)
Work done by B in 1 day = 1/15 – 1/25 = 2/75
=> B can complete the work in 75/2 days = 37 ½ days

849. 12 buckets of water fill a tank when the capacity of each bucket is 13.5 litres. How many buckets will be needed to fill the same tank, if the capacity of each bucket is 9 litres?
A. 14
B. 15
C. 16
D. 18

Explanation:
Capacity of the tank = (12×13.5)=162 litres
Capacity of each bucket = 9 litres.
Number of buckets needed = 162/9=18

850. A leak in the lower portion of a tank can empty the full tank in 9 hrs. An inlet pipe fills water at the rtae of 10 lit. a minute. When the tank is full, the inlet is opened and due to leak, the tank is empty in 16 hrs. How many litres does the cistern hold ?
A. 12,342 litres.
B. 12,444 litres
C. 12,566 litres.
D. None of these

NOTE
IF YOU THINK ANY OF THE MCQ ABOVE IS WRONG.
PLEASE COMMENT WITH CORRECT ANSWER AND ITS DETAIL EXPLANATION IN COMMENT BOX.
THANK YOU