Question

a, b, and c can do a piece of work in 15, 20, and 12 days respectively. they began the work together but a left 5 days before completion of the work. in how many days was the work done?

Answer 1

total work..LCM of 15,20,12=60
hence ..a,b,c efficiency is..a=4,b=3,c=5
a,t,q last five. days b and c work together

therefore work done by b and c together is..(5+3)×5=40unit work complete in 5 days
and remain work is 60-40=20
this remaining 20 unit is done by a,b and c together
time taken 20÷12=5/3
hence total time taken 5+5/3=18/3 ans