Practice Equations with Missing Numbers for 11 Plus

21 October 2026

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Equations and missing numbers explained

Understanding how to solve equations and find missing numbers is a core skill for the 11+ maths exam.

Key insight: Missing number questions test logical thinking and the ability to work backwards using opposite operations.

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What is a missing number in an equation

A missing number is an unknown value in a maths problem. It is often shown as a blank, a box, or a letter such as x or n. The goal is to find which value makes the equation true.

How to approach these questions

Start by looking at the equation and identifying which number is missing. Use the opposite operation to isolate the missing number. For example, if the equation uses addition, use subtraction to find the answer.

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Worked example

3x + 4 = 19

First, subtract 4 from both sides: 19 - 4 = 15

Next, divide both sides by 3: 15 ÷ 3 = 5

The correct answer is x = 5.

Step-by-step approach

1. Write down the equation clearly.

2. Use the opposite operation to move numbers away from the side with the unknown.

3. Work one step at a time until only the missing number is left.

4. Check your answer by putting it back into the original equation.

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Why practice matters

Regular practice with equations and missing numbers helps children build confidence and accuracy. These skills support wider problem-solving abilities needed for the 11+ exam.