A task is completed by $15$ men in $16$ days. How many men will be needed to complete ${\left(\frac{1}{4}\right)}^{\mathrm{th}}$ of the task in $15$ days?

A camp of $120$ soldiers has sufficient provisions for $60$ days. If after $40$ days, $40$ soldiers were deputed elsewhere, how long will the remaining provisions last for the remaining soldiers?

If $11$ spiders spin $11$ webs in $11$ days then how many webs will one spider spin in one day?

Two taps together fill a tank in $6$ hours. One of the taps alone fills it in $10$ hours. How long will it take to fill the tank if only the second tap is open?