What is the minimum number of days that they will take to finish the work?

Question

When working alone A, B and C can complete a piece of work in 10, 15 and 20 days respectively. At the most only two people can work on each day and nobody works more than two consecutive days. What is the minimum number of days that they will take to finish the work?

1.   6 days
2.   6(2/3) days
3.   6(4/5)days

Answer 1

Option C) 6(4/5) days

Comments

please give a soltuion..

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No one works for 2 consecutive days means we can allow A B and C to work like following
First day A and B works Second day A+C works and third day B+C works and then again the cycle goes

So in three days days they complete (13/30) part of work done
Next 3 days Total work done = 26/30 part

Remaining 1-(26/30) = (4/30) part

A and B takes (4/5 ) time to complete it
So 3+3+4/5 = 6(4/5) days