$A$ can do a piece of work in $30$ days while $B$ can do it in $40$ days. In how many days can $A$ and $B$ working together do it?

$45$ men can complete a work in $16$ days. Four days after they started working,$36$ more men joined them. How many days will they now take to complete the remaining work?

If $6$ men and $8$ boys can do a piece of work in $10$ days and $26$ men and $48$ boys can do the same work in $2$ days,the time taken by $15$ men and $20$ boys to do the same type of work will be (in days)

Ram,Rajan,and Rangan can do a certain work in $6, 12,$ and $24$ days respectively. In what time will they altogether do it? (in days)

$7$ men can complete a piece of work in $12$ days. How many additional men will be required to complete double the work in $8$ days?

$A$ and $B$ can do a piece of work in $45$ days and $40$ days respectively. They began to do the work together,but $A$ leaves after some days and then $B$ completed the remaining work in $23$ days. The number of days after which $A$ left the work was: