Four litres of milk are to be poured into a 2-litre bottle and a 4-litre bottle. If each bottle is to be filled to the same f...

Four litres of milk are to be poured into a 2-litre bottle and a 4-litre bottle. If each bottle is to be filled to the same fraction of its capacity, how many litres of milk should be poured into the 4-litre bottle?