  # Understand Simple Algebraic Substitution

In this worksheet, students will substitute numbers for letters and work out the value of simple expressions with one variable. Key stage:  KS 3

Curriculum topic:   Algebra

Curriculum subtopic:   Substitute Numerical Values for Formulae/Expressions

Popular topics:   Algebra worksheets, Year 7 Algebra worksheets

Difficulty level:   #### Worksheet Overview

When we substitute a number for a letter, we simply replace the letter with the number.

However, we must remember that 4b means 4 x b.

Example

Work out the value of the following expression when a = 4

3a - 7

3a - 7

3a just means 3 x a , so we have

3 x a - 7

Change the letter (a) into the number we've been given (4)

3 x 4 - 7

Now multiply first - remember the order of BIDMAS (or BODMAS)

12 - 7 = 5

Did that make sense?

The key to substitution in algebra is to work slowly, one step at a time.

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