Checking and securing understanding of substitution | Maths

Starter quiz

Simplify the following: $3(2x + 1) + 2(2x + 1) = \square(2x + 1)$

'5' ✓
Simplify the following: $4(x - 3) + 3(x - 3) = \square(x - 3)$

'7' ✓
If $b = 9$ , what is $b^2$ ?

'81' ✓
If $p = 9$ , what is $2p^2$ ?

'162' ✓
If $c = 4$ , what is $4c + 3$ ?

'19' ✓
If $c = 4b + 2$ , what is $3c$ ? Give your answer in expanded form.

'12b + 6' ✓

Exit quiz

Evaluate the expression $2x - 3$ for $x = 5$

'7' ✓
Evaluate the expression $\frac{3x}{4}$ for $x = 8$

'6' ✓
Evaluate the expression $4x^2$ for $x = 3$

'36' ✓
Evaluate the expression $5(x - 3)$ for $x = 7$

'20' ✓
Evaluate the expression $\frac{3x + 2}{4}$ for $x = 6$

'5' ✓
Evaluate the expression $\frac{x}{x + 1}$ for $x = 4$ and give your answer as a decimal.

'0.8' ✓

Worksheet

Loading worksheet ...

Presentation

Loading presentation ...

Video

Lesson Details

Key learning points

Expressions and formulae in context can be evaluated for particular values.
Changing the value of the variable changes the overall value of the expression.
Exploring what value gives a particular solution can help you to understand the expression.
Expressions may have multiple variables and you can substitute some or all of them for numbers.

Common misconception

Incorrect evaluation of expressions is common when negative values are substituted. Especially where negative values are squared or pupils rely on calculators without being confident of their use.

When substituting, always put brackets around the value which is substituted. This helps avoid mistakes when using a calculator as well.

Keywords

Substitution - Substitute means to put in place of another. In Algebra, substitution can be used to replace variables with values.