$A$ can do a piece of work in $15 \text{ days}$. With the help of $A$,$B$ can do it in $6 \frac{2}{3} \text{ days}$. $B$ can do it alone in (in $\text{days}$)

$7$ men can complete a piece of work in $12$ days. How many additional men will be required to complete double the work in $8$ days?

$A$ completes a piece of work in $4 \text{ days}$ and $B$ completes it in $6 \text{ days}$. If they both work on it together,then the number of days required to complete the same work is (in $\text{days}$):

$P$ and $Q$ together can do a job in $6$ days. $Q$ and $R$ can finish the same job in $60/7$ days. $P$ started the work and worked for $3$ days. $Q$ and $R$ continued for $6$ days. Then the difference of days in which $R$ and $P$ can complete the job is

$12$ men and $16$ boys can do a piece of work in $5$ days. $13$ men and $24$ boys can do it in $4$ days. Then,the ratio of the daily work done by a man to that of a boy is:

$A$ 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?