A, B, C can do a piece of work alone in 10, 12, 15 days respectively. At the most only two people can work on each day

A, B, C can do a piece of work alone in 10, 12, 15 days respectively. At the most only two people can work on each day and nobody works for more than two consecutive days. What is the minimum number of days that they will take to finish the work?

Sol:

Ist day A + B 22

IInd day A + B 22

IIIrd day B 8/52*2

6 days _______ 104 unit

Remaining work =11/22 of days

Total time = 6 8/11days