Ratio and proportion

For grown-ups: this lesson in words

Year 6 · Maths

Ratio and proportion: I can write a ratio, scale it up, find a scale factor and share an amount in a ratio.

1. Mei makes a pattern with 2 red circles and 3 blue circles.

   For every 2 red circles there are 3 blue circles.

   We write the ratio of red to blue as 2 : 3

   Say it as 2 to 3. Red is named first, so 2 comes first.

   Picture: Red: 2 red circles and Blue: 3 blue circles.

2. Mei makes the pattern twice: 2 red, 3 blue, 2 red, 3 blue.

   2 + 2 = 4 red circles. 3 + 3 = 6 blue circles.

   Both numbers are multiplied by 2: 2 × 2 = 4 and 3 × 2 = 6

   4 : 6 is the same ratio as 2 : 3. There are still 2 red for every 3 blue.

   Picture: 2 red circles, 3 blue circles, 2 red circles and 3 blue circles.

3. Your turn: Kofi's bowl has 3 apples and 1 pear. What is the ratio of apples to pears?

   Picture: Apples: 3 apples and Pears: 1 pear.

   Choose one:

   • 1 : 3
   • 3 : 1
   • 3 : 4

   Answer

   The answer: 3 : 1

   Apples to pears is 3 : 1. There are 3 apples, then 1 pear.

Words to know

ratio:

Compares two amounts in order: 2 red for every 3 blue is written 2 : 3.

scale factor:

How many times longer every side of a shape has become.

part:

One share in a ratio. In 2 : 3 there are 5 parts altogether.