Question

A boy and a girl together fill a cistern with water. The boy pours 4 litres of water every 3 minutes and the girl pours 3 litres every 4 minutes. How much time will it take to fill 100 litres of water in the cistern?

Answer 1

Answer:

48 minutes

Step-by-step explanation:

The boy pours 4 litres of water every 3 minutes.

From that we can know, Boy can pour 4/3 litres for every 1 minute.

The girl pours 3 litres every 4 minutes.

From that we can know, Girl can pour 3/4 litres for every 1 minute.

Let x be the time required.

$\frac{4}{3} x + \frac{3}{4} x = 100 \\ \\ \frac{25x}{12} = 100 \: \: \: \: \: \: \: \: \: \: \: \\ \: \: \: \: \: \: \: \: \: \: \\ x = 48 \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$

48 minutes required for them to fill 100 litres in cistern