This sequence explores ratios through the context of mixing paint. Students recognise that ratios express a multiplicative relationship between two measures and that the numerical values of both quantities need to change by the same factor for the proportion to remain constant (**covariation**).

This sequence is for students who have a knowledge of multiplication.

### Lesson 1: Mixing Paint

Students mix two batches of pink paint, one batch mixing red and white paint in the ratio 1:2 and the other batch in the ratio 1:5. They explore how to keep the ratio constant when increasing the quantity of red or white paint.

### Lesson 2: Adding Parts

Students are posed with the scenario of painting a wall using a mixture of blue and white paint in the ratio of 1:3. They determine if adding an extra tin of each colour changes the ratio.

### Lesson 3: Fairer Shares

This task presents the context of combining two equal sized tins containing different shades of green paint. One tin contains a mixture of green and white paint in the ratio of 1:3, the second tin a mixture in the ratio of 1:7. Students determine the resulting ratio of green to white paint when the two tins are combined.

Last updated April 28 2020.