Three pumps

We are filling the pool. The first pump would be filled in 12 hours, the second pump in 15 hours. If all three pumps were running at the same time, it would fill the pool for 4 hours. How long would the pool fill only with the third pump?

Correct answer:

x =  10 h

Step-by-step explanation:

$$\begin{gathered} 4\cdot ({\displaystyle \frac{1}{12}}+{\displaystyle \frac{1}{15}}+{\displaystyle \frac{1}{x}})=1 \\ 4\cdot (x\mathrm{/}12+x\mathrm{/}15+1)=x \\ 24x=240 \\ x=10=10\text{ h} \end{gathered}$$

Try another example

Related math problems and questions:

• Pumping
  The tank is filled with a larger pump in 12 hours and with scond pump in 15 hours. For how long does the tank fill when both pumps are switched on at the same time?
• Tributaries
  The first tributary fill pool with water in 15 hours. The second tributary fill pool in 10 hours. For how many hours the pool is filled with both tributaries?
• Two pumps
  The first pump fills the tank in 24 hours second pump in another 40 hours. For how long will it take to fill the tank if it operates both pumps at the same time?
• Oil tank and pipes
  The underground oil tank can be filled by two oil pipelines. The first is filled in 72 hours and the second in 48 hours. How many hours from the moment when first pipeline began to fill the oil is it necessary to start filling it with the second to fill i
• Three pumps
  The water tank is emptied with the first pump in 6 hours, with the second pump in 2 hours. In order to be emptied in 1 hour, all three pumps had to be started at once. How long will take tank be emptied by only the third pump?
• Two pumps
  Pump A takes twice as long to fill a tank as B. Together they take 2 hours to fill the tank. How long does each one take to fill the tank by itself?
• Pumps
  First pump flows 16 liters per second into the basin by the second pump 75% of the first and by third pump half more than the second. How long will take fill basin by all three pumps simultaneously volume 15 m³ (cubic meters)?
• Pumps 3
  Two pumps of the same power fill the garden pool for 10 hours. How many of these pumps would have to use if we want to shorten the filling of the pool to four hours?
• Pool 2
  The first supply by the pool fill for five hours and the second fill for six hours, drain should be drained for 15 hours. For how many hours the pool is full, when we open both inlet now and outlet open two hours later?
• Three tributaries
  It is possible to fill the pool with three tributaries. The first would take 12 hours, the second 15 hours, and the third 20 hours. The day before the summer season began, the manager opened all three tributaries simultaneously. How long did it take to fi
• Tank 9
  The tank with volume V is filled with one pump for three hours and by the second pump for 5 hours. When both pumps run simultaneously, calculate: a) how much of the total volume of the tank is filled in one hour b) for how long is the tank full
• Two tributaries
  Two tributaries of the pool fill it in 10 hours. One of the tributaries would fill 15 hours. How long would fill the first tributary?
• Two pumps together
  The first pump will fill the tank itself in 3 hours and the second one in 6 hours. How many hours will the tank be full if both pumps are worked at the same time?
• Five pumps
  Three same pumps fill the tank with 50400 liters of diesel in 7 hours. How many liters of diesel will it take in 4 hours if we add two more of the same pumps and pump them the same way? How much more (or less) will they get if we add 2 of the same pumps a
• Pool
  Pool is filled with two water supply. The first supply fill pool for nine hours, the second for six hours. How many hours will take fill the pool when the water flows in through the first supply 3 hours and then we will open a second supply?
• Two pipes
  How long will the pool be filled with a double supply pipe if it takes the pool to fill the first pipe by 4 hours longer and the second pipe 9 hours longer than both pipes open at the same time?
• Water reservoir
  The water reservoir is filled with one pump for 4 days by the second one for 9 days. Outlet can drain tank in 12 days. How long take fill the reservoir if both pumps are running and not closed outlet channel.