Question

A, B and C can do a job in 12 h, 20 h and 30 h respectively. If they all work together, how long will they take to complete the job?​

Answer 1

A = 12 hours

B = 20 hours

C = 30 hours

let us consider that total work is = 60 unit (by lcm)

If total work is 60 unit and a can do it in 12 hours

means = 60/12 = 5 unit work per hour

similarly => B = 60/20 = 3 unit work per hour

=> C = 60/30 = 2 unit of work per hour

total work of one hour = 5+3+2 = 10 unit

=> 60/10=6 hours