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

Ram can finish a work in $15 \text{ days}$ working $8 \text{ hrs/day}$. Fari can finish it in $6 \frac{2}{3} \text{ days}$ at $9 \text{ hrs/day}$. Find in how many days both can finish it together,if both work $10 \text{ hrs/day}$?

$A$ can complete a piece of work in $10$ days,while $B$ alone can complete it in $15$ days. They work together for $5$ days and the rest of the work is done by $C$ in $2$ days. If they receive $Rs. 450$ for the whole work,how should they divide the money? (in $Rs.$)

$A$ contract is to be completed in $92$ days and $234$ men were set to work,each working $16$ hours a day. After $66$ days,$\frac{4}{7}$ of the work is completed. How many additional men may be employed,so that the work may be completed in time,each man now working $18$ hours a day?

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

$A$ and $B$ together can complete a work in $3$ days. They start together,but after $2$ days,$B$ left the work. If the work is completed after two more days,in how many days would $B$ alone do the work?