  # Understand Direction Proportion

In this worksheet, students will be asked to resolve problems related to direct proportion. Key stage:  KS 3

Curriculum topic:   Ratio, Proportion and Rates of Change

Curriculum subtopic:   Solve Problems Involving Direct and Inverse Proportion

Difficulty level:   #### Worksheet Overview

Direct proportion refers to the relationship between two variables where their ratio is equal to a constant value.

Example:

Given that y is directly proportional to x and that x = 19 when y = 133.

Find:
(i) a formula connecting y and x
(ii) the value of y when x = 13
(iii) the value of x when y = 119

y ∝ x

So, y = kx for a constant k.

(i) Given x = 19, when y = 133,

133 = k x 19

k = 133 ÷ 19 = 7

Therefore, the formula is y = 7x

(ii) When x = 13, y = 7 x 13 = 91

(iii) When y = 119, x = 119 ÷ 7 = 17

It's useful to have paper and a pencil in order to record your own workings.

These are not the kind of questions you can calculate mentally.

Over to you!

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