a b and c can do a piece of work in 30 45 and 90 days in how many days

Total Unit 90
A->30 takes 3
B->45 takes 2
C->90 takes 1
3 days A alone works means 3*3= 9 Unit
and in 4th day A+B+C all works so = 6 unit
means on 4th days total 15 units were completed
so to complete 90 unit we nee 6*4 = 24 days(Answer){15on 4th, 30 on 8th, 45 on 12, 60 on 18th....).
10 years agoHelpfull: Yes(7) No(0)
work done by 'a' each day would be 1/30.
work done by 'b and c' together in a day is (1/45)+(1/90)=1/30.
A good approach would be,
To find out how many 4 day intervals are there,
(30/4) = 7.5, that would be 7 days.
But on 1st day a is not helped, so that would be 7-1 = 6 days.
On those days work achieved is = each day work of 'a' and 'b' &'c'
=(1/30)+(1/30) = 2/30
this happens 6 times so 6*(2/30) = 12/30.
rest work left 18/30, for which a takes 18 days. so total days a takes to complete the work would be (6+18) = 24 days.
10 years agoHelpfull: Yes(2) No(0)
A's 3 day work=1/30*3= 1/10
(A+B+C) 1 day work = 1/15
So, total 4days work= 1/10+1/15= 1/6
therefore total days = 6*4=24
10 years agoHelpfull: Yes(1) No(1)
total work is done in 24days.
10 years agoHelpfull: Yes(1) No(2)

a, b and c can do a piece of work in 30,45, and 90 days.in how many days a alone do the work if he is assited by b and c on every 4th day?