A, B and C can do a piece of work in 10, 20 and 30 days, respectively. In how many days can A do the work if he is assisted by B and C on every third day?

$8 \frac{2}{11}$ days

A = 10 days, B = 20 days, C = 30 days,

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

 1st day = 6 units,

 2nd day = 6 units,

 3rd day = 6 + 3 + 2 = 11 units

Every 3 days, 23 units are completed,

So, In 6 days, 46 units of work is completed,

and In 8 days, 58 units of work is completed,

Therefore, in \( {8 }_{11 }^{2 } \) days, 60 units will be completed.