$A$ certain sum of money is sufficient to pay wages for $21$ days of $X$ or $28$ days of $Y$. The money is sufficient to pay the wages of both for ........ days.

$2$ men and $4$ boys can do a piece of work in $10$ days,while $4$ men and $5$ boys can do it in $6$ days. Men and boys are paid wages according to their output. If the daily wage of a man is $Rs. 40$,then the ratio of daily wages of a man and a boy will be

$A$ and $B$ can together finish a work in $30$ days. They worked at it for $20$ days and then $B$ left. The remaining work was done by $A$ alone in $20$ more days. $A$ alone can finish the work in (in days):

$A$ 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?

Heena can do a work in $20$ days,while Himani can do the same work in $25$ days. They started the work jointly. $A$ few days later,Mayuri also joined them,and thus all of them completed the whole work in $10$ days. All of them were paid a total of $Rs. 700$. What is the share of Mayuri (in $Rs.$)?

Anu can complete a work in $10$ days. Manu is $25\%$ more efficient than Anu,and Sonu is $60\%$ more efficient than Manu. Working together,how long would they take to finish the job? (in days)