Question

A,b and c can do a piece of work in 40 days,30 days and 60 days respectively.A work continuously,on every third day a is assisted by b and



c.In how many days work is completed

Answer 1

LCM of 40, 30 and 60 is 120

So we will take total work to be 120 units.

A = 120/40 = 3 units/day

B = 120/30 = 4 units/day

C = 120/60 = 2units/day

Now A is working two days alone and on third day B and C are joining him and this goes on and on until work is done.
Day 1 = A’s work = 3 units

Day 2 = A’s work = 3units

Day 3 = (A + B +C) ‘ s work = 3 + 4 + 2 =9 units
So this is a set of 3 days in which total 3+3+9 = 15units work is being done.

Now to complete 120 units, 120/15= 8 such sets of 3 days are needed.

8 sets of 3 days means 8*3 = 24days