Question

A,B and C can complete a work in 10,15 and 20 days respectively .If all of them work together to complete the work what fraction of work would have done by B​

Answer 1

no. of days in which A complete work =10

amount of work done by A in 1day=1/10

no. of days in which B complete work =15

amount of work done by B in 1day=1/15

no. of days in which C complete work =20

amount of work done by C in 1day=1/20

no. of days in which they together complete work =(1/10+1/15+1/20)^-1=(13/60)^-1=60/13

fraction of work done by B=60/13×1/15=4/13