Question

Two pipes a and b can fill a crystals in 24 minutes and 32 minutes respectively if both the pipes are opened together then after how many minutes should be closed so that the tank is full in 18 minutes

Answer 1

Answer:

So, B must be closed after 8 mins for the tank to be filled in 18 mins.

Step-by-step explanation:

This method is not sacrosanct, but the whole purpose is to solve quickly,hence the technique. You may use fractions but I find it tedious and too bookish.

Let the capacity of the tank be 96 L ( LCM of 24 & 32 ) .You can assume any other number which is a multiple of these two numbers.

Hence, rate of filling of water by tap A = 96 / 24 = 4 L/min,

Similarly, for B( rate of filling) = 96 / 32 = 3 L / min

Since A is open for 18 mins water filled by it = 18 *4 = 72 L

Water filled by B = 96 -72 = 24 L ,so the time for which it was open = 24 / 3 = 8 mins.

So, B must be closed after 8 mins for the tank to be filled in 18 mins.