Substitution 2.

Formula Expressed In Words. Example 1. There are four prongs on a fork. How many prongs on 12 forks. Solution. The formula for the number of prongs is : We have 12 forks Prongs = 4 x number of forks Prongs = 4 x 12 = 48 prongs

Example 2. A baker can place 5 pizzas on a baking tray. How many baking trays will he need for 45 pizzas? Solution. The formula for the number of baking trays required is : Baking trays = number of pizzas  5 You have 60 pizzas Baking trays = 60  5 = 12

Example 3. The cost of hiring a video is £5 to join the video shop and £3 for each video hired. Calculate the cost of hiring 7 videos. Solution. The formula for the cost of hiring videos is: Cost = £3 x number of videos + £5 to join shop. You have hired 7 videos. Cost = 3 x 7 + 5 = £26

Example 4. How long to cook a 8kg chicken if to cook a chicken at gas mark 6 you give it 10 minutes per kilogram and an extra 20 minutes at the end to make sure it’s fully cooked. Solution. The formula to cook a chicken is : Time = 10 x number of kg’s + 20 minutes extra. Your chicken weights 8 kg. Time = 10 x 8 + 20 = 100 minutes