861. A can lay a railway track between two given stations in 16 days and B can do the same job in 12 days. With help of C, they did the job in 4 days only. Then, C alone can do the job in_________?
A. 4
B. 9.6
C. 9
D. 10

Explanation:
Part of work completed by A and B in 4 days
= 4*((1/16) + (1/12))
= 7/12 C can complete 5/12th of the work in 4 days C can complete the whole job in
4÷(5/12) = 9.6 days

862. If 10 bulls can plough 20 identical fields in 3 days working 10 hours a day, then in how many days can 30 bulls plough 32 same identical fields working 8 hours a day?
A. 2
B. 8
C. 10
D. 12

Explanation:
M1*D1*W2 = M2*D2*W1
10*3*10*32 = 30*d*8*20
d = 2 days

863. A work can be finished in 16 days by twenty women. The same work can be finished in fifteen days by sixteen men. The ratio between the capacity of a man and a woman is_________?
A. 1:3
B. 4:3
C. 2:3
D. 2:1

Explanation:
Work done by 20 women in 1 day = 1/16
Work done by 1 woman in 1 day = 1/(16×20)
Work done by 16 men in 1 day = 1/15
Work done by 1 man in 1 day = 1/(15×16)
Ratio of the capacity of a man and woman =1/(15×16) : 1/(16×20) = 1/15 : 1/20
= 1/3 :1/4 = 4:3

864. P, Q and R can complete a work in 24, 6 and 12 days respectively. The work will be completed in________days if all of them are working together.
A. 2
B. 3 3⁄7
C. 4 ¼
D. 5

Explanation:
Work done by P in 1 day = 1/24
Work done by Q in 1 day = 1/6
Work done by R in 1 day = 1/12
Work done by P,Q and R in 1 day = 1/24 + 1/6 + 1/12 = 7/24
=> Working together, they will complete the work in 24/7 days = 3 3⁄7 days

865. Two pipes P and Q can fill a cistern in 12 minutes and 16 minutes respectively. Simultaneously both the pipes are opened together, then after how much time Q should be closed so that the tank is full in 9 min ?
A. 2 min
B. 3 min
C. 4 min
D. 5 min

Explanation:
Let Q be closed after x min. Then part filled by (P+Q) in x min + part filled by P in ( 9 – x )min
x(1/12+1/16)+(9−x)1/12=1

866. A can do a certain job in 12 days. B is 60% more efficient than A. The number of days it takes for B to do the same piece of work, is:_________?
A. 12/6 days
B. 15/2 days
C. 23 days
D. 34 days

Explanation:
Ratio of time, taken by A and B = 160 : 100 = 8 : 5
If A takes 8 days, B takes 5 days.
If A takes 12 days, B takes = [5/8×12]=15/2 days

867. A can do piece of work in 30 days while B can do it in 40 days. In how many days can A and B working together do it ?
A. 70 days
B. 120/7 days
C. 50 days
D. 45 days

868. A and B can do a piece of work in 21 and 24 days respectively. They start the work together and after some days, A leaves and B completes the rest of the task in 9 days. After how many days did A leave?
A. 5
B. 6
C. 7
D. 8

Explanation:
Part of work completed by A in a day = 1/21 Part of work completed by B in a day = 1/24 Part of work completed by them together in a day = (1/21)+(1/24)
= 5/56 Part of work completed by B in 9 days
= 9/24 = 3/8 If A left after x days,
(5x/56)+(3/8) = 1
x = 7

869. A,B,C, can do a work in 8,14,16 days respectively. A does the work for the first 2 days. B continues from it and finishes 2/3rd of the remaining work. C finishes the remaining work. How many days would have taken to complete the work?
A. 13
B. 11
C. 12
D. 15

Explanation:
A completes 2*(1/8) = 1/4th of the work 2/3rd of the remaining work
= (3/4) * (2/3) = 1/2 B completes 1/2 of the work in
(1/2)÷(1/14) = 7 days C completes 1/4th of the work in
(1/4)÷(1/16) = 4 days They take 13 days to complete the work

870. If 6 men working together can complete 50 identical tasks in 4 hours then how many such identical tasks can be completed if 10 men are working together for 6 hours?
A. 20
B. 25
C. 125
D. 60

Explanation:
M1*D1*W2 = M2*D2*W1
Where, M – number of people working
D – time of work
W – number of tasks or work
6*4*W2 = 10*6*50