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Prerequisites

- A1a – Using and interpreting algebraic notation (essential)
- N9b – Multiplying and dividing in standard form (helpful for Exam-style question 5)

# Substituting numerical values into formulae and expressions

Click the tabs for extension tasks…

- Find a possible value of \(n\) so that \(n+7\) is less than \(2n\).
- Find a possible value of \(n\) so that \(n+7\) is more than \(2n\).
- Find the value of \(n\) such that \(n+7=2n\).

- Find a possible value of \(x\) so that \(x+8\) is less than \(3x\).
- Find a possible value of \(x\) so that \(x+8\) is more than \(3x\).
- Find the value of \(x\) such that \(x+8=3x\).
- Can you find the value of \(x\) such that \(x+7=3x\)?

- Find a set of values of \(p\), \(q\), and \(r\) such that \(\dfrac{p+q}{r}=1\), where \(p\), \(q\), and \(r\) are positive integers.
- Find a
*different*set of values of \(p\) \(q\), and \(r\) such that \(\dfrac{p+q}{r}=1\), where \(p\), \(q\), and \(r\) are positive integers. - Find a set of values of \(p\), \(q\), and \(r\) such that \(\dfrac{p+q}{r}=1\)
**and**\(p+q+r=25\).

Teacher resources

Links to past exam questions

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In the real world

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What next?

Substitution is a fundamental skill in algebra, along with solving equations. You will use it in many contexts. Two basic situations in which you will use substitution are (1) to plot a graph given its equation and (2) to use formulas to work out some useful information, such as the area of a shape: