$A$ tank can be filled by pipe $A$ in $2$ $hours$ and pipe $B$ in $6$ $hours.$ At $10 \, am$ pipe $A$ was opened. At what time will the tank be filled if pipe $B$ is opened at $11 \, am$?

Two pipes $A$ and $B$ can fill a tank in $36$ $hours$ and $45$ $hours$ respectively. If both the pipes are opened simultaneously,how much time (in $hours$) will be taken to fill the tank?

Two taps $A$ and $B$ can fill a tank in $10$ $hours$ and $12$ $hours$ respectively. If both taps are opened at $10 \text{ am}$,at what time (in $\text{pm}$) should tap $A$ be closed so that the tank is completely filled at exactly $4 \text{ pm}$?

Inlet $A$ is four times faster than inlet $B$ to fill a tank. If inlet $A$ alone can fill it in $15$ minutes,how long will it take if both the pipes are opened together? (in minutes)

Two taps can separately fill a cistern in $10$ $minutes$ and $15$ $minutes$ respectively. When the waste pipe is open,they can together fill it in $18$ $minutes$. The waste pipe can empty the full cistern in:

An empty pool being filled with water at a constant rate takes $8$ $hours$ to fill $\frac{3}{5}$ of its capacity. How much more time will it take to finish filling the pool?