If $10$ persons can do a job in $20$ days,then $20$ persons with twice the efficiency can do the same job in (in days)

$P$ and $Q$ together can do a job in $6$ days. $Q$ and $R$ can finish the same job in $60/7$ days. $P$ started the work and worked for $3$ days. $Q$ and $R$ continued for $6$ days. Then the difference of days in which $R$ and $P$ can complete the job is

$A$ can finish a work in $24$ days,$B$ in $9$ days,and $C$ in $12$ days. $B$ and $C$ start the work but are forced to leave after $3$ days. The remaining work was done by $A$ in (in days):

$20$ women together can complete a work in $16$ days. $16$ men together can complete the same work in $15$ days. The ratio of the working capacity of a man to that of a woman is

Working $7\, \text{hours}$ daily,$24$ men can complete a piece of work in $27$ $\text{days}$. In how many $\text{days}$ would $14$ men complete the same piece of work working $9\, \text{hours}$ daily?

$A, B$ and $C$ can do a piece of work in $20, 30$ and $60$ days respectively. In how many days can $A$ do the work if he is assisted by $B$ and $C$ on every third day?