To make a jam you mix sugar and fruit in the ratio of 4:3. How much fruit do you use in making 420 g of jam?
To make a garden spray you mix up the insecticide with water in the ratio of 1: 9. How much water to you use in making up 2 litres of the spray?
Fat and flour are mixed to make a pastry in the ratio of 1:4. How much flour do you use in making 600 g of the pastry?