$A, B$ and $C$ individually can do a work in $10\, days, 12\, days$ and $15\, days,$ respectively. The number of days required to finish the work by $A, B$ and $C$ working together is? (in $days$)

$15$ men take $20$ days to complete a job working $8$ hours a day. The number of hours a day $20$ men should work to complete the same job in $12$ days is:

Sunil completes a work in $4$ days,whereas Dinesh completes the work in $6$ days. Ramesh works $1 \frac{1}{2}$ times as fast as Sunil. The three together can complete the work in (in days):

$A$ and $B$ together can complete a work in $12$ days. $A$ alone can complete it in $20$ days. If $B$ does the work only for half a day daily,then in how many days will $A$ and $B$ together complete the work?

If $A$ works alone,he would take $4$ days more to complete the job than if both $A$ and $B$ worked together. If $B$ worked alone,he would take $16$ days more to complete the job than if $A$ and $B$ work together. How many days would they take to complete the work if both of them worked together?

$A$ and $B$ together can complete a work in $10$ days. They started together,but $A$ left after $2$ days and the remaining work was completed by $B$ in $12$ days. In how many days can $A$ complete the entire work while working alone?