# Solve Problems Involving Missing Ratios

In this worksheet, students will solve assorted problems using ratios.

Key stage:  KS 3

Curriculum topic:   Ratio, Proportion and Rates of Change

Curriculum subtopic:   Use Ratio Notation

Difficulty level:

#### Worksheet Overview

In this activity, we will use what we know about ratio to solve some problems with some algebra in there!

Eek!

Not to worry, we'll soon get this sorted. Let's check out an example.

Example

If we say x:y = 2:3

We can also say that

Or, we can multiply through by y, then again by 3 and get

This can help us if we had a missing value!

Let's look at a possible question.

Question

​(x + 1):9 = 2:3

Find x.

We can also say:

We can multiply through by 3 and 9 to give us:

Multiply out the bracket to form an equation::

Now we can solve it to find x!

Subtract 3 from both sides

Divide through by 3

We can check it by using 5 in the question:

We know that 6/9 simplifies to 2/3 so we are correct!!!!

Phew - that was a lot of work! The best way to get our heads around this is to practise doing some!

So, let's get started!

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