$A$ can do a piece of work in $20$ days and $B$ in $30$ days. They work together for $7$ days and then both leave the work. Then $C$ alone finishes the remaining work in $10$ days. In how many days will $C$ finish the full work?

Shashi can do a piece of work in $20$ days. Tanya is $25\%$ more efficient than Shashi. The number of days taken by Tanya to do the same piece of work is

$A, B$ and $C$ can do a piece of work individually in $8, 10$ and $15$ days respectively. $A$ and $B$ start working,but $A$ quits after working for $2$ days. After this,$C$ joins $B$ until the completion of the work. In how many days will the work be completed?

$P, Q$ and $R$ undertake to do a work for $Rs. 660$. $P$ and $Q$ together do $8/11$ of the work and the rest is done by $R$ alone. How much should $R$ get? (in $Rs.$)

$X$ and $Y$ can do a piece of work in $20$ days and $12$ days respectively. $X$ started the work alone and then after $4$ days $Y$ joined him until the completion of the work. How long did the work last? (in days)

If $3$ men and $4$ boys can earn $Rs. 2100$ in $7$ days,and $11$ men and $13$ boys can earn $Rs. 8300$ in $8$ days,in what time will $7$ men and $9$ boys earn $Rs. 11000$? (in days)