How do i weigh 40 litres of water from two jericans of 30 and 50 litres respectively?

Question

water volume in two jericans

Answer 1

40 liters av water=40 kg, yu dont need tu wae it

Answer 2

Assume that 2 empty cans, a 30l-can and a 50l-can, are kept on standby, but no scale is on hand.

1. Fill 50l-can with water to capacity, and then remove the water in 50l-can into 30l-can to capacity: 30l-can is full and 50l-can holds 20 litres of water inside.

2. Empty 30l-can, and then remove 20 litres of water left in 50l-can into 30l-can: 30l-can holds 20 litres of water inside and 50l-can is empty.

3. Fill 50l-can with water to capacity again, and then remove the water in 50l-can into 30l-can to capacity: 10 litres of water in 50l-can is removed into 30l-can.

Now we have 40 litres of water in 50l-can and 30 litres of water in 30l-can.