$39$ persons can repair a road in $12$ days working $5$ hours per day. In how many days will $30$ persons working $6$ hours per day complete the same work?

$A$ piece of work was to be completed in $40$ days. $A$ number of men employed upon it did only half the work in $24$ days. $16$ more men were then set on,and the work was completed in the specified time. How many men were employed at first?

$A$ 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?

$A$ works thrice as good as $B$ and is,therefore,able to finish a piece of work in $60 \text{ days}$ less than $B$. Find the time in which they can complete it,working together (in $\text{days}$).

Akka can bake $100$ cakes in $20$ hours. Akka and Tai together can bake $75$ cakes in $10$ hours. How many cakes can Tai bake in $20$ hours?

$X$ is three times as fast as $Y$ and is able to complete the work in $40 \text{ days}$ less than $Y$. Then the time in which they can complete the work together is (in $\text{days}$)