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.
4
B.
5
C.
6
D.
7
Answer: Option A
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
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.
13
C.
17
D.
21
Answer: Option B
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
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
Answer: Option A
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
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
Answer: Option A
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.
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 ?
