Direct Proportion Thursday, 18 April 2019 Unitary Methods Direct Proportion Thursday, 18 April 2019

Example If 5 books cost £30, find the cost of 8 books 5 books = £30 30 1 book = = £6 5 8 books = 6 x 8 = £48

Example If 7 pens cost 63 pence, find the cost of 12 pens. 7 Pens = 63 63 1 pen = 9 pence 7 12 pens = 9 x 12 = 108 pence

Example If 12 calculators cost £72, find the cost of 9 calculators. 12 Calculators = £72 72 1 Calculator = £6 12 9 Calculators = 6 x 9 = £54

Example If a machine takes 20 seconds to make 8 components, how long will it take to make 16 components? 20 components? (i) 16 components = 2 x 20 = 40 seconds (ii) 8 components = 20 20 1 component = = 2.5 8 20 components = 2.5 x 20 50 seconds

Example A plane flies 50 km in 15 minutes. a) How long will it take to fly 300 km? b) How many kilometres will it fly in 24 minutes? a) 50 km = 15 mins b) 15 minutes = 50 km 15 50 1 km = = 0.3 1 minute = = 10/3 50 15 300km = 0.3 x 300 = 90 minutes 24 minutes = 10/3 x 24 = 80 km