Answer: If the ratio of 1:4 Cordial and water mixture is a total of 1 L, then you need a ration of 2:8 Cordial mixture two make 2 Liters mixture.
Explanation: In every 1 Cordial mixture, there is added 4 mixtures of water. (I suppose the 1:4 ratio is 1 L together). To make two Liters, we need twice as many proportions. That would mean we will need a ratio of 2:8 of cordial and water.
If I misunderstood the problem, please explain the 1:4 ratio. I need to know how many Liters is the 1:4 ratio. Is it 1/4 of a liter? 1:4 adding up to 1 Liter?
If we don't know how much Liters are in that ratio, we can't find how much Liters of mixture we need to add of both Cordial and Water to make a mixture of 2 Liters.