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Solved examples on Time and Work:
Question: Mohan can do a piece of work in
10 days and Ramesh can do same work in 15 days.
How long will they take if both work together?
Solution:
(10*15)/(10+15) =6 days
Question: A and B together can complete a piece
of work in 4 days, If A alone can complete the
same Work in 12 days, in how many days can B
alone complete that work?
Solution:
(12*4)/(12-4)= 6 days
Question: A and B can do a piece of work in 18 days;
B and C can do it in 24 days; A and C can do it in 36 days.
In how many days will A, B and C ?nish it. Working together
and separately?
Solution:
Twice of work done by A, B and C
together=72/(4+3+2)=8 days
(72 being lcm of 18,24,36)
So A B and C together can do that work in 16 days.
Time taken by A = (24*16)/(24-16)=48 days
Time taken by B = (36*16)/(36-16)= 144/5 days=28 4/5 days
Time taken by C = (18*16)/(18-16)= 144 days
Question: A and B working separately can do a piece of work in
9 and 12 days respectively. If they work for a day alternately,
A beginning, in how many days, the work will be completed?
Solution:
A+B ‘s 2-day work = 7/36
10 days (5 pairs) of combined work =35/36
Work left=1/36 which is to be done by A in 1/36 divided
by 1/9 i.e. 1/4 days
Hence, total time taken is 10 ¼ days
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