A fruit drink recipe for 5 servings uses 1.2 litres of water. How many litres are needed for 12 servings with unchanged proportions? Enter the number of litres.

Explanation

The water per serving is 1.2 divided by 5, or 0.24 litres, so 12 servings need 2.88 litres. Adding the seven extra servings to 1.2 would give 8.2, which wrongly treats servings as litres rather than scaling the ingredient.