Subhash can copy $50$ pages in $10$ $h$,Subhash and Prakash can copy $300$ pages in $40$ $h$. In how much time can Prakash copy $30$ pages? (in $h$)

$A$ and $B$ together can complete a piece of work in $12$ days and $B$ and $C$ together in $15$ days. If $A$ is twice as good a workman as $C$,then in how many days will $B$ alone complete the same work?

$A$ can finish a work in $18$ days and $B$ can do the same work in $15$ days. $B$ worked for $10$ days and left the job. In how many days can $A$ alone finish the remaining work?

$A$ can do a piece of work in $30$ days,$B$ in $50$ days,and $C$ in $40$ days. If $A$ is assisted by $B$ on one day and by $C$ on the next day alternately,the work will be completed in (in days):

$4$ men and $6$ women together can complete a work in $8$ days,while $3$ men and $7$ women together can complete it in $10$ days. How many days will $20$ women working together take to complete the same work?

$A$ can do a piece of work in $4 \, days$ and $B$ can do it in $12 \, days.$ In how many $days$ will they finish the work,both working together?