P takes twice as much time as Q or thrice as much time as R to finish a piece of work. They can finish the work in 2 days if work together. How much time will Q take to do the work alone?
A.
2 days
B.
4 days
C.
6 days
D.
8 days
Answer: Option C
Explanation:
Let P takes x days to complete the work Then Q takes x/2 days and R takes x/3 days to finish the work Amount of work P does in 1 day = 1/x Amount of work Q does in 1 day = 2/x Amount of work R does in 1 day = 3/x Amount of work P,Q and R do in 1 day = 1/x + 2/x + 3/x = 1/x (1 + 2 + 3) = 6/x 6/x = 2 => x = 12 => Q takes 12/2 days = 6 days to complete the work
3 men and 7 women can complete a work in 10 days . But 4 men and 6 women need 8 days to complete the same work . In how many days will 10 women complete the same work?
A.
20
B.
30
C.
40
D.
50
Answer: Option C
Explanation:
Work done by 4 men and 6 women in 1 day = 1/8 Work done by 3 men and 7 women in 1 day = 1/10 Let 1 man does m work in 1 day and 1 woman does w work in 1 day. The above equations can be written as 4m + 6w = 1/8 —(1) 3m + 7w = 1/10 —(2) Solving equation (1) and (2) , we get m=11/400 and w=1/400 Amount of work 10 women can do in a day = 10 × (1/400) = 1/40 Ie, 10 women can complete the work in 40 days
P, Q and R can do a work in 20, 30 and 60 days respectively. How many days does it need to complete the work if P does the work and he is assisted by Q and R on every third day?
A tank can be filled by a pipe in 20 min. and by another pipe in 60 min. Both the pipes are kept open for 10 min. and then the first pipe is shut off. After this, the tank will be completely filled in?
