How many $days$ will $1648$ persons take to construct a dam,if $721$ persons can build the same in $48$ 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

$45$ men can complete a work in $16$ days. Four days after they started working,$36$ more men joined them. How many days will they now take to complete the remaining work?

If $12$ men and $16$ boys can do a piece of work in $5 \, \text{days}$,and $13$ men and $24$ boys can do it in $4 \, \text{days}$,then the ratio of the daily work done by a man to that of a boy is:

$A$ and $B$ working separately can do a piece of work in $9$ and $15 \, \text{days}$ respectively. If they work on alternate days beginning with $A$,then the work will be completed in how many days?

$A$ 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 $\text{days}$)