A tap fills a tank in $6$ hr. After half the tank is filled, three more similar taps are opened. The total…
A tap fills a tank in $6$ hr. After half the tank is filled, three more similar taps are opened. The total time taken to fill the tank is:
$3$ hr $15$ min
$3$ hr $30$ min
$3$ hr $45$ min
$4$ hr
Solution
Half the tank by $1$ tap takes $3$ hr. Then $4$ taps fill the remaining half: combined rate $= \dfrac{4}{6} = \dfrac{2}{3}$ tank/hr. Time $= \dfrac{1/2}{2/3} = \dfrac{3}{4}$ hr $= 45$ min. Total $= 3$ hr $45$ min.