$2$ men alone or $3$ women alone can complete a piece of work in $4$ days. In how many days can $1$ woman and $1$ man together complete the same piece of work?

$A$ can complete a piece of work in $40$ days. He starts working,but having some other engagements,he leaves after $5$ days. Thereafter,$B$ completes the remaining work in $21$ days. How many days would $A$ and $B$ take to complete this work working together?

$A$ and $B$ undertook to do a piece of work for $Rs. 4500$. $A$ alone could do it in $8$ days and $B$ alone in $12$ days. With the assistance of $C$,they finished the work in $4$ days. Then,$C$'s share of the money is (in $Rs.$)

If $4$ men or $8$ women can do a piece of work in $15$ days,in how many days can $6$ men and $12$ women do the same piece of work?

$A, B$ and $C$ together can complete a piece of work in $30\, min$. $A$ and $B$ together can complete the same work in $50\, min$. $C$ alone can complete the work in? (in $min$)

$10$ men working $6\, \text{h}$ a day can complete a work in $18\, \text{days}$. How many $\text{hours per day}$ must $15$ men work to complete the same work in $12\, \text{days}$?