$15$ men take $20$ days to complete a job working $8$ hours a day. How many hours a day should $20$ men work to complete the same job in $12$ days?

$A$ can do a piece of work in $24$ days,$B$ in $32$ days,and $C$ in $64$ days. All begin to do it together,but $A$ leaves $6$ days before the completion of the work. How many days did the work last?

$A$'s $2$ days work is equal to $B$'s $3$ days work. If $A$ can complete the work in $8$ days,then to complete the work $B$ will take (in days):

$3$ persons undertake to complete a piece of work for $Rs. 1,200$. The $first$ person can complete the work in $8$ days,the $second$ person in $12$ days,and the $third$ person in $16$ days. They complete the work with the help of a $fourth$ person in $3$ days. What does the $fourth$ person get? (in $Rs.$)

Ramesh takes twice as much time as Mahesh and thrice as much time as Suresh to complete a job. If working together,they can complete the job in $4 \, \text{days}$,then the time taken by each of them separately to complete the work is (in $\text{days}$)

$A$ and $B$ can do a job in $6$ and $12$ days,respectively. They began the work together,but $A$ leaves after $3$ days. Then,the total number of days needed for the completion of the work is: