A ,B and C can do a piece of work in 10, 15 and 30 days, respectively. If B and C both assist A on every third day, then in how many days will 40% of the work be completed?
the amount A can do in one day is 1/10
The amount all three can do in a day is 1/10 + 1/15 + 1/30 = 1/5
so, in three days, the amount done will be 1/10 + 1/10 + 1/5 = 2/5 = 40%