871. P works twice as fast as Q. If Q alone can complete a work in 12 days, P and Q can finish the work in________days
A. 1
B. 2
C. 3
D. 4

Explanation:
Work done by Q in 1 day = 1/12
Work done by P in 1 day = 2 × (1/12) = 1/6
Work done by P and Q in 1 day = 1/12 + 1/6 = ¼
=> P and Q can finish the work in 4 days

872. P is 30% more efficient than Q. P can complete a work in 23 days. If P and Q work together, how much time will it take to complete the same work?
A. 9
B. 11
C. 23
D. 13

Explanation:
Work done by P in 1 day = 1/23
Let work done by Q in 1 day = q
q × (130/100) = 1/23
=> q = 100/(23×130) = 10/(23×13)
Work done by P and Q in 1 day = 1/23 + 10/(23×13) = 23/(23×13)= 1/13
=> P and Q together can do the work in 13 days

873. 6 men and 8 women can complete a work in 10 days. 26 men and 48 women can finish the same work in 2 days. 15 men and 20 women can do the same work in_______days.
A. 4 days
B. 6 days
C. 2 days
D. 8 days

Explanation:
Let work done by 1 man in 1 day = m and work done by 1 woman in 1 day = b
Work done by 6 men and 8 women in 1 day = 1/10
=> 6m + 8b = 1/10
=> 60m + 80b = 1 — (1)
Work done by 26 men and 48 women in 1 day = 1/2
=> 26m + 48b = ½
=> 52m + 96b = 1— (2)
Solving equation 1 and equation 2. We get m = 1/100 and b = 1/200
Work done by 15 men and 20 women in 1 day
= 15/100 + 20/200 =1/4
=> Time taken by 15 men and 20 women in doing the work = 4 days

874. A cistern has two taps which fill it in 12 min. and 15 min.respectively There is one outlet pipe in the cistern. When all the taps & pipe are opened, the empty cistern is full in 20 min. How long will the waste pipe (outlet) take to empty the full cistern ?
A. 10 min
B. 20 min
C. 30 min
D. 40 min

Explanation:
Work done by waste pipe in 1 minute
=1/20−(1/12+1/15)=−1/10
Waste pipe will empty the full cistern in 10 minutes.

875. To fill a cistern, pipes P, Q & R take 20, 15 & 12 minutes respectively. The time in minutes that the three pipes together will take to fill the cistern is:__________?
A. 5 min
B. 10 min
C. 15 min
D. 20 min

876. A alone can finish a work in 10 days and B alone can do it in 15 days. If they work together and finish, then out of a total wages of Rs.75. A will get:___________?
A. 35 Rs.
B. 40 Rs.
C. 45 Rs.
D. None of these

Explanation:
Ratio of time taken by A and B= 10 : 15 = 2 : 3
Ratio of work done in the same time = 3:2, So, the money is to be divided among A and B in the ratio 3 : 2
A’s share = Rs. [75×3/5] = Rs.45.

877. 2 men and 12 women can finish a job in 4 days. 4 men and 6 women can do the same job in 5 days. Find the time taken by 1 man and 1 woman to complete the job.
A. 30 days
B. 25 days
C. 24 days
D. 20 days

Explanation:
Part of work done by 1 man in a day = 1/m Part of work done by 1 woman in a day
= 1/w (2/m)+(12/w) = (1/4) (4/m)+(6/w) = (1/5) Solving,
1/m = 1/40 ,1/w = 1/60 (1/m)+(1/w) = 5/120 = 1/24

878. Bilal can do a work in 15 days and Jalal in 12 days. If they work on it together for 4 days, the fraction of work that is left is________?
A. 3/5
B. 4/7
C. 2/5
D. 1/4

Explanation:
Part of work completed by Bilal in a day = 1/15 Part of work completed by Jalal in a day = 1/12 Part of work completed by them in a day = (1/15)+(1/12) = 3/20 Part of work completed by them in 4 days = (3/20)*4 = 3/5 Fraction of work left
= 1-(3/5)
= 2/5

879. A and B can finish a piece of work in 20 days .B and C in 30 days and C and A in 40 days. In how many days will A alone finish the job?
A. 48
B. 34(2/7)
C. 44
D. 45

Explanation:
(1/A)+(1/B) = (1/20) (1/B)+(1/C) = (1/30) (1/A)+(1/C) = (1/40) Solving the three equations,
A=48

880. If X and Y complete a certain work in 10 days, Y and Z in 16 days and X and Z in 22 days, find the time required for each one to complete the work while working separately.
A. 120, 40, 60 days
B. 120, 60, 80 days
C. 40, 30, 120 days
D. 30, 40, 60 days

Explanation:
Let a: be the time in which X & Y completes their work = 30 days
b: time in which Y & Z completes their work = 24 days
c: time in which X & Z completes their work = 40 days
X alone can complete the work in (2 * a * c) / (ab + bc – ac) days
= 2 * 30 * 24 * 40 / ((30 * 24) + (24 * 40) – (30 * 40)) = 120 days
Y alone can complete the work in 2 * a * b * c / (- ab + bc + ac) days
= 2 * 30 * 24 * 40 / (-(30 * 24) + (24 * 40) + (30 * 40)) = 40 days
Z alone can complete the work in 2 * a * b * c / (ab – bc + ac) days
= 2 * 30 * 24 * 40 / ((30 * 24) – (24 * 40) + (30 * 40))
= 60 days

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