Free IB Maths AA SL lesson: Ratio & proportion
A ready-to-teach IB Maths AA SL lesson on Ratio & proportion (Unit 0 · Prior knowledge): editable slides and teacher notes, free; a printable worksheet in 3 levels with answers for school plans. About 55 minutes.
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What's inside
- Slides (PowerPoint, editable) · freeabout 12 slides: do now, objectives, key ideas, a worked example step by step, “your turn”, practice QR code, exit ticket
- Teacher notes (PDF) · freelesson plan with timings, common mistakes, homework links
- Worksheet (PDF) · school plans6 questions, 12 marks: Fluency, Reasoning, Exam-style. Included with school plans and the teacher trial.
- Answers (PDF) · school plansthe answer to every worksheet question, from its mark scheme. Included with school plans and the teacher trial.
Learning objectives
- Ratio
Key ideas on the slides
- Simplify a ratio by dividing every part by the same number; write the parts in the same units first.
- To share an amount in the ratio a:b, find the value of one part: total ÷ (a+b), then multiply by a and by b.
- If you know one share, find one part from it: in 3:5, if the larger share is 40, one part is 8.
- A ratio a:b means the first quantity is a/(a+b) of the total.
By the end of the lesson, students should be able to answer a question like: Share £60 in the ratio 2 : 3.
Key vocabulary
- ratio: A comparison of the sizes of two or more quantities.
- part: One unit of a ratio; the total is split into equal parts.
- unitary method: Finding the value of one unit (or part) first, then scaling up.
- directly proportional: y = kx: when one quantity is multiplied by a number, so is the other.
- constant of proportionality: The fixed number k in the formula.
Common mistakes this lesson tackles
- Dividing the total by one number of the ratio instead of by the sum of the parts.
- Treating a ratio 2:3 as the fractions ⅔ and 3/2 of the total.
- Simplifying ratios with mixed units, such as 50 cm : 2 m as 25 : 1.
- Using y = x + k instead of y = kx.
Calculator tips
- Use the fraction key to find one part, then multiply; check that the shares add up to the total.
- Store k in memory so later values are exact.
Lesson plan
| 0–5 min | Do now: students write down what they remember about Fractions, decimals & percentages and Number operations & order of operations (BIDMAS) |
| 5–8 min | Share the learning objective and success criteria |
| 8–20 min | Teach: the worked example, step by step; students copy the method |
| 20–25 min | Your turn: 1 mini-whiteboard question; check every board before moving on |
| 25–42 min | Practise: the worksheet (6 questions in 3 levels, with school plans and the teacher trial) or the topic's practice questions online; move up a level after two right in a row |
| 42–47 min | Plenary: 1-question exit ticket; collect it to plan the next lesson |
For students: practise this topic
The worksheet's QR code opens the Prior Knowledge practice questions.
What schools get
- Set this lesson as homework, marked by AI against the mark scheme, with every result in your markbook (with a School plan).
- This lesson's worksheet in three levels, with its answers, ready to print.
- Support, Core and Stretch versions and A/B copies of the worksheet from the full question bank, in the worksheet builder.
- Create lesson: this lesson rebuilt for your class's next scheme-of-work lesson, from the full bank.
School licences from €490 a year. Try everything free for 30 days as a teacher: no card.
Questions teachers ask
Is this lesson free?
The slides and the teacher notes are free to download with a free IB Math Revision teacher account (sign in with Google, Microsoft or email); no card. The printable worksheet in three levels and its answers are included with school plans and the free 30-day teacher trial.
Can I edit the slides?
Yes. The slides are an ordinary PowerPoint file: change, add or delete anything. They also open in Google Slides and Keynote. The logo and web address sit on the slide master, so your edits do not move them.
What do students use for homework?
The practice slide's QR code and web address take students to the Prior Knowledge practice questions on ibmathrevision.com, where the free questions are open and the full bank comes with a plan.