A, B and C can complete a work alone in 400, 600 and 900 days respectively. In how many days can the work be completed if it is started by A and he is assisted by B and C on every second and third day respectively?

292

A = 400 days, B = 600 days, C = 900 days,

⇒ A starts the work and he is assisted by B and C on every second and third day respectively,

 1st day = 9 units,

 2nd day = 9 + 6 = 15 units,

 3rd day = 9 + 4 = 13 units,

Every 3 days = 37 units of work done,

So, in 291 days, 3589 units of work will be completed,

And in 292 days, 3598 units of work will be completed,

Therefore, total work will be completed in \( { 292}_{ 15}^{ 2} \) days    ̴  292 days,