Question

cistern can filled with water by an inlet pipe in 25 minutes and outlet pipe in 45 minutes.if both the pipes are opened together ,then in what time will the cistern be full of water

in answersheet this is coming 224/4 mins but I don't know how this ans is coming . I have told the ans so that you can match. and solve it easily.kindly give full eexplaination


who ever will give the correct ans definitely I will mark him or her as brainliest

Answer 1

Answer:

Let t = time it takes to empty tank

then

1 - t(1/30) + t(1/45) = 0

1 - t/30 + t/45 = 0

multiplying both sides by (30)(45):

1350 - 45t + 30t = 0

1350 - 15t = 0

1350 = 15t

90 minutes = t

Step-by-step explanation:

Now, A full tank can be emptied in 30 minutes if the drain is opened

so in one minute V/30 liters will be drained.

and an empty tank can be filled in 45 minutes with the inlet pipe opened

so in one minute V/45 litres will be filled into the tank.

now both pipes are opened when the tank is full.

when both pipes are opened per minute V/45 litres enter and V/30 litres exit the tank.