A jar contains a blend of a fruit juice and water in the ratio 5 : x
Quantity of fruit juice in 4 litres of blend = 4[5/(5 + x)] = 20/(5 + x)
⇒ Quantity of water in 4 litres of blend = 4[x/(5 + x)] = 4x/(5 + x)
According to questions
20/(5 + x) : {4x/(5 + x) + 1} = 1 : 1
⇒ 20 - 4x = 5 + x
x = 3