A and B together can do a piece of work in 25 days. If
B works alone for the last 10 days, it is completed in
30 days. In
how
many days A alone can do it?
Answers
Answer:
Step-by-step explanation:
A and B can together complete a work in 25 days.
In 1 day A and B does: 1/25 work.
Its said, the work is completed in 30 days, if B works alone for last 10 days.
Means, A and B together worked for 20 days. Then A alone worked to complete the work in 30 days.
A and B in 20 days do: 30* 1/25 = 1.5 work
Work remaining = 1 - 1.5 = -0.5 work
-0.5 work done by A in 10 days
-0.5== 10 days
1== X
X = 60 days.
A can complete the work alone in 60 days.
In 1 day A does: 1/60 work.
Let in 1 day B does 1/b work
1/25 = 1/60 + 1/b
1/b = 1/25 - 1/60 = 0.00066666666
b = 90 days.
Hence B can complete the work alone in 90 days.
Hope it helps.
SHORT CUT
A+B=== 25 days
A completed the work alone in last 10 days and the work was competed in 40 days.
WORK REMAINING:
A+B A
6 days 10 days
L.C.M(6.10) = 30 = Remaining work
A+B effic = 30/6 =5
A's effic = 30/10 = 3
Hence, B's effic = 5-3 = 2 [efficiencies are constant hence doesn't matter whether its determined from total work or remaining work)
TOTAL WORK = TOTAL EFFICIENCY * DAYS
TOTAL WORK = 5*36 = 180
B's time(days) = Work/ffic = 180/2 = 90 days.
Answer:
See, The answer should be 12 days
As If there r 2 persons A..B so if both can do a piece of work in 25 days. One can do 12 (25/2)