Two women,Sita and Gita,working separately can mow a field in $8$ and $12 \, hrs$ respectively. If they work in stretches of one hour alternatively,with Sita beginning at $9:00 \, a.m.$,when will the mowing be finished? (in $p.m.$)

Two workers $A$ and $B$ working together completed a job in $5$ days. If $A$ worked twice as efficiently as he actually did and $B$ worked $\frac{1}{3}$ as efficiently as he actually did,the work would have completed in $3$ days. Find the time for $A$ to complete the job alone (in days).

$A, B$ and $C$ can do a piece of work individually in $8, 12$ and $15$ days,respectively. $A$ and $B$ start working,but $A$ quits after working for $2$ days. After this,$C$ joins $B$ until the completion of the work. In how many days will the work be completed?

$A$ 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.

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)

How many $days$ will $1648$ persons take to construct a dam,if $721$ persons can build the same in $48$ days?