831. P and Q can complete a work in 20 days and 12 days respectively. P alone started the work and Q joined him after 4 days till the completion of the work. How long did the work last?
A. 5 days
B. 10 days
C. 15 days
D. 12 days

Explanation:
Work done by P in 1 day = 1/20
Work done by Q in 1 day = 1/12
Work done by P in 4 days = 4 × (1/20) = 1/5
Remaining work = 1 – 1/5 = 4/5
Work done by P and Q in 1 day = 1/20 + 1/12 = 8/60 = 2/15
Number of days P and Q take to complete the remaining work = (4/5) / (2/15) = 6
Total days = 4 + 6 = 10

832. P can finish a work in 18 days. Q can finish the same work in 15 days. Q worked for 10 days and left the job. how many days does P alone need to finish the remaining work?
A. 8
B. 6
C. 4
D. 2

Explanation:
Work done by P in 1 day = 1/18
Work done by Q in 1 day = 1/15
Work done by Q in 10 days = 10/15 = 2/3
Remaining work = 1 – 2/3 = 1/3
Number of days in which P can finish the remaining work = (1/3) / (1/18) = 6

833. P can lay railway track between two stations in 16 days. Q can do the same job in 12 days. With the help of R, they completes the job in 4 days. How much days does it take for R alone to complete the work?
A. 9(3/5) days
B. 9(1/5) days
C. 9(2/5) days
D. 10 days

Explanation:
Amount of work P can do in 1 day = 1/16
Amount of work Q can do in 1 day = 1/12
Amount of work P, Q and R can together do in 1 day = 1/4
Amount of work R can do in 1 day = 1/4 – (1/16 + 1/12) = 3/16 – 1/12 = 5/48
=> Hence R can do the job on 48/5 days = 9 (3/5) days

834. wo pipes X and Y fill a tank in 15 hrs. and 20 hrs. respectively, while a third pipe ‘Z’ can empty the full tank in 25 hrs. All the three pipes are opened in the beginning. After 10 hrs. Z is closed. In how much time, will the tank be full ?
A. 12 hrs
B. 14 hrs
C. 16 hrs
D. 18 hrs

Explanation:
Part filled in 10 hrs.
= 10[1/15+1/20−1/25]=23/30

835. 8 men can dig a pit in 20 days. If a man works half as much again as a boy, then 4 men and 9 boys can dig a similar pit in:__________?
A. 12 days
B. 16 days
C. 18 days
D. 20 days

836. Efficiency of Rashid and Danish are in the ratio 5:8. If Danish takes 51 days less than Rashid to complete the work, find the time taken by Rashid to complete the work.
A. 85 days
B. 126 days
C. 118 days
D. 136 days

Explanation:
Time taken is inversely proportional to their efficiency. So, time taken is in the ratio 8:5. Time taken by Rashid to finish the work = 8x Time taken by Danish to finish the work = 5x 8x-5x=51 3x=51 x=17 8x=136

837. If 12 men work 8 hours a day to complete a work in 10 days, how many men working 12 hours a day can complete the work in 5 days?
A. 16
B. 4
C. 12
D. 8

Explanation:
12 men work 8 hours for 10 days x men work 12 hours for 5 days x = (12*8*10)/(12*5) = 16 men

838. If daily wages of a man is double to that of a woman, how many men should work for 25 days to earn Rs.14400? Given that wages for 40 women for 30 days are Rs.21600.
A. 15
B. 14
C. 16
D. 13

839. Mansoor-Ul-Haque and Aaqib are working on a special assignment. Mansoor-Ul-Haque needs 6 hours to type 32 pages on a computer and Aaqib needs 5 hours to type 40 pages. If both of them work together on two different computers, how much time is needed to type an assignment of 110 pages?
A. 7 hour 15 minutes
B. 7 hour 30 minutes
C. 8 hour 15 minutes
D. 8 hour 30 minutes

Explanation:
Pages typed by Mansoor-Ul-Haque in 1 hour = 32/6 = 16/3
Pages typed by Aaqib in 1 hour = 40/5 = 8
Pages typed by Mansoor-Ul-Haque and Aaqib in 1 hour = 16/3 + 8 = 40/3
Time taken to type 110 pages when Mansoor-Ul-Haque and Aaqib work together = 110 × 3 /40 = 33/4
= 8 ¼ hours = 8 hour 15 minutes

840. 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 the same in 12 hours. All the machines started printing at 9 A.M. Machine P is stopped at 11 A.M. and the remaining two machines complete work. Approximately at what time will the printing of one lakh books be completed?
A. 3 pm
B. 2 pm
C. 1:00 pm
D. 11 am

Explanation:
Work done by P in 1 hour = 1/8
Work done by Q in 1 hour = 1/10
Work done by R in 1 hour = 1/12
Work done by P,Q and R in 1 hour = 1/8 + 1/10 + 1/12 = 37/120
Work done by Q and R in 1 hour = 1/10 + 1/12 = 22/120 = 11/60
From 9 am to 11 am, all the machines were operating.
Ie, they all operated for 2 hours and work completed = 2 × (37/120) = 37/60
Pending work = 1- 37/60 = 23/60
Hours taken by Q an R to complete the pending work = (23/60) / (11/60) = 23/11
which is approximately equal to 2
Hence the work will be completed approximately 2 hours after 11 am ; ie around 1 pm

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