Question

A works in n +80 days and B in n+20 days. In how many days will the work be completed I.e find n?

Answer 1

a+b can do it in 40 days..

task completed in 10 day = 1/4th of the whole

3/4th part of the work done by a+b+c in 20 daysthen these three can complete a whole amount of work in 20 x4/3=80/3 days

now talking of the efficiency of all three

a+b    &      a+b+c

40                80/3

120              80      lcm 240

2-effe           3-effe

effe of c=1

then b-effe=1/3

1+1/3+a's effe=3

a effe= 5/9

time taken by a=240/5 x 9=48x9=432days.