Ruchi, Khushi and Teju can do a piece of work in 30, 40 and 60 days respectively. In how many days can Ruchi do the work, if she is assisted by both Khushi and Teju on every third day ?

$\frac{85}{4}$ days

Ruchi = 30D, Khushi = 40D, Teju = 60D

Since Ruchi is working daily and Khushi & Teju assist her on every third day, the efficiencies will be as follows:

1st day (Ruchi) = 4

2nd day (Ruchi) = 4

3rd day (All) = 4 + 3 + 2 = 9  

Every 3 days work = 4 + 4 + 9 = 17

Hence, in 21 days, 119 units of work will be completed

The remaining work i.e; 1 unit will be completed by Ruchi in \(\frac{1}{4}\)days.

Therefore, The Total time taken to complete work will be \( { 21}_{ 4}^{1 } \)=  \(\frac{85}{4}\)Days.