(B) Let the capacity of the cistern be the Least Common Multiple $(LCM)$ of $12, 15,$ and $20,$ which is $60$ units. Efficiency of the first tap = $6

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(B) Let the capacity of the cistern be the Least Common Multiple $(LCM)$ of $12, 15,$ and $20,$ which is $60$ units. Efficiency of the first tap = $60 / 12 = 5$ units/min. Efficiency of the second tap = $60 / 15 = 4$ units/min. When all pipes are open, the net efficiency = $60 / 20 = 3$ units/min. Let the efficiency of the waste pipe be $x$ units/min. Then, $5 + 4 - x = 3$. $9 - x = 3$, which gives $x = 6$ units/min. Time taken by the waste pipe to empty the full cistern = $\text{Total capacity} / \text{Efficiency of waste pipe} = 60 / 6 = 10$ minutes.

Competitive Quantitative Aptitude Pipes and Cistern Pipes and Cistern

Easy

$A$ cistern has two taps which fill it in $12$ $minutes$ and $15$ $minutes,$ respectively. There is also a waste pipe in the cistern. When all the pipes are opened, the empty cistern is full in $20$ $minutes.$ How long will the waste pipe take to empty a full cistern?

A
$8 \text{ minutes}$
B
$10 \text{ minutes}$
C
$12 \text{ minutes}$
D
$16 \text{ minutes}$

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Pipes and Cistern

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Pipes and Cistern

$A$ water tank has two taps $A$ and $B$. Tap $A$ can fill it in $6$ hours,and tap $B$ can empty it in $5$ hours. If both taps are opened simultaneously,how much time (in hours) is required to empty the tank?

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Three taps are fitted to a cistern. The empty cistern is filled by the first and second taps in $3$ and $4 \, h$,respectively. The full cistern is emptied by the third tap in $5 \, h$. If all three taps are opened simultaneously,the empty cistern will be filled up in?

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$A$ leak in the bottom of a tank can empty the full tank in $8$ $hours$. An inlet pipe fills water at the rate of $6$ $litres$ a minute. When the tank is full,the inlet pipe is opened and due to the leak,the tank is empty in $12$ $hours$. How many litres does the tank hold?

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$A$ cistern has two pipes. One can fill it in $8 \, h$ and the other can empty it in $5 \, h$. In how many $hours$ will the cistern be emptied if both the pipes are opened together when $\frac{3}{4}$ of the cistern is already full of water?

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$A$ tap having diameter $d$ can empty a tank in $40$ $min$. How long will another tap having diameter $2d$ take to empty the same tank (in $min$)?

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$A$ cistern has two taps which fill it in $12$ $minutes$ and $15$ $minutes,$ respectively. There is also a waste pipe in the cistern. When all the pipes are opened, the empty cistern is full in $20$ $minutes.$ How long will the waste pipe take to empty a full cistern?

Similar Questions

$A$ water tank has two taps $A$ and $B$. Tap $A$ can fill it in $6$ hours,and tap $B$ can empty it in $5$ hours. If both taps are opened simultaneously,how much time (in hours) is required to empty the tank?

Three taps are fitted to a cistern. The empty cistern is filled by the first and second taps in $3$ and $4 \, h$,respectively. The full cistern is emptied by the third tap in $5 \, h$. If all three taps are opened simultaneously,the empty cistern will be filled up in?

$A$ leak in the bottom of a tank can empty the full tank in $8$ $hours$. An inlet pipe fills water at the rate of $6$ $litres$ a minute. When the tank is full,the inlet pipe is opened and due to the leak,the tank is empty in $12$ $hours$. How many litres does the tank hold?

$A$ cistern has two pipes. One can fill it in $8 \, h$ and the other can empty it in $5 \, h$. In how many $hours$ will the cistern be emptied if both the pipes are opened together when $\frac{3}{4}$ of the cistern is already full of water?

$A$ tap having diameter $d$ can empty a tank in $40$ $min$. How long will another tap having diameter $2d$ take to empty the same tank (in $min$)?

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