Question

23)
A and B can separately complete a
piece of work in 20 days and 30 days
respectively. They worked together for
some time, then B left the work. If A
completed the rest of the work in 10 days,
then B worked for
a) 6 days
b) 8 days
c) 12 days
d) 16 days
​

Answer 1

The answer is Option (a) 6 days....

A's 10 days work = 10×3 units/ days = 30 units

So,(60−30)=30 units of work would have been done by A

and B both and it took time:

30(3+2)=6days

So, B worked for 6 days

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Answer 2

Given

A completes a piece of work in = 20 days

B completes the same piece of work = 30 days

Now as mentioned in the question the rest of the work is to be completed 10 days.

Thus, number of days required  by A to complete the work in reaming 10 days will be = 10/20 days = 1/2 days

similarly

number of days required  by A and B together to complete the remaining work =(1/2)/(1/20+ 1/30) = 6 days