Concepts

● Proportion is an equation stating that two ratios or rates are equivalent. It can be written in two ways: as two equal fractions ab = cd; or using a colon, a:b = c:d.

● Rate – A ratio that compares two quantities with different kinds of units.

● Rate of change – a rate that describes how one quantity changes in relation to another.

● Constant rate of change – two variables have a constant rate of change if the ratio of one variable to the other is proportional.

Rules

If x and y have a proportional relationship, the constant rate of change is the ratio of y to x.

Rate of change = yx

Example

Choose the correct rate of change between the two quantities shown in the table.

Solution

1. Calculate the ratio of y to x.

Rate of change = 62 = 3

2. The rate of change is $ 31 balloon.

Answer: 

Pre-requisite Skills

Simplify Fractions (6.4.4)

Understand Ratios (6.6.1)

Ratios and Fractions (6.6.2)

Ratio Applications (6.6.11)

Unit Rate Applications (6.6.12)

Proportional Relationships Applications (6.6.13)