Year 9 - Maths
Changing the subject with simple formula
Expressions and formulae
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit develops pupil understanding of formulae and how to rearrange them. Pupils will learn how to recognise and manipulate binomials and learn to recognise the difference of two squares.
Lesson Summary
You will learn to apply an understanding of inverse operations to a simple formula in order to make a specific variable the subject.
Key Notes
- Changing the subject can be thought of as solving an equation in one unknown.
- Throughout the rearrangement, the expressions on each side of the equals sign remain equal.
- Changing the subject can offer different perspectives on the relationship.
- It can make it easier to calculate the unknown value if that is the subject.
Vocabulary To Learn
- Formula: A formula is a rule linking sets of physical variables in context. The plural of formula is formulae.
- Subject: The subject of an equation/a formula is a variable that is expressed in terms of other variables. It should have an exponent of 1 and a coefficient of 1.
Common Mistakes To Avoid
- The subject of a formula is just the first term in the formula.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
Changing the subject can be thought of as solving an equation in one unknown. Throughout the rearrangement, the expressions on each side of the equals sign remain equal.
2. Use this key word in a maths sentence and explain it clearly. 'Formula'
A formula is a rule linking sets of physical variables in context. The plural of formula is formulae. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: The subject of a formula is just the first term in the formula. Correction: Draw attention to the variety of equations and formulae used in the lesson.
More Lessons In This Unit
- Additive relationships Study Guide
- Changing the subject to suit the context Study Guide
- Changing the subject with more complex formula Study Guide
- Checking and securing solving linear equations Study Guide
- Checking and securing understanding of the distributive law with algebraic terms Study Guide
- Difference of two squares Study Guide
- Evaluating expressions with and without changing the subject Study Guide
- More complex binomial products Study Guide
- Multiplicative relationships between terms Study Guide
- Problem solving with expressions and formulae Study Guide
- The product of two binomials Study Guide
Browse all guides in the Year 9 Maths guide library.