​Learning Objectives

​• simplify and compare ratios

​• divide an amount into two parts in a given ratio

​• use the unitary method to solve problems involving ratio and direct proportion

​12.1 Simplifying Ratios

The ratio of red to yellow is 1 : 3​

1 : 3 is read as "1 to 3"

​A ratio written in its simplest form must not contain any decimals or fractions.

​12.2 Sharing in Ratios

​12.2 Sharing in Ratios

​12.3 Using Direct Proportion

​Two quantities are in direct proportion when their ratio stays the same as the quantities increase or decrease.

​

​One packet of rice costs $3.25, so two packets of rice cost twice as much.

​Two packets of rice cost 2 × $3.25 = $6.50.

​

Six tickets to a concert cost $120, so three tickets cost half as much.

Three tickets cost $120 ÷ 2 = $60.

​The method used in part a is called the unitary method because you find the cost of one book then use this to find the cost of 10 books.

​egg : cupcake = 2 : 12 = 1 : 6

​So, 1 egg is for 6 cupcake

​

​36 : 6 = 6 OR 6 eggs are needed to make 36 cupcakes

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