$10$ men can complete a piece of work in $15$ days and $15$ women can complete the same work in $12$ days. If all the $10$ men and $15$ women work together,in how many days will the work get completed?

Five men and $2$ boys,working together,can complete four times as much work per hour as a man and a boy working together. The ratio of the work completed by a man and a boy is:

$A$ and $B$ working separately can do a piece of work in $9$ and $12$ days,respectively. If they work for a day alternately with $A$ beginning,the work would be completed in (in days):

$A$ 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?

$18$ boys can do a piece of work in $24$ days. In how many days can $27$ boys do the same work?

$A$ contract is to be completed in $92$ days and $234$ men were set to work,each working $16$ hours a day. After $66$ days,$\frac{4}{7}$ of the work is completed. How many additional men may be employed,so that the work may be completed in time,each man now working $18$ hours a day?