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Compound measures

Compound measures for A Level History OCR: what it means, how to set the working out, and the questions it is asked in.
  • A Level
  • OCR
  • History
  • Spec A4 · A20 · A3
  • 14 min read
  • 7 revision boxes

Introduction

2 boxes
1 min read

What is compound measures?

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Transcript

A short spoken summary of compound measures and where it is used.

A spoken walk-through of compound measures before you read the notes.
This idea appears again in the higher-mark questions, so it is worth over-learning.
Worth knowing: 49=7\sqrt{49} = 7.
2 rows

The compound measures reference table

The examiner marks the working, so a correct answer with no method still drops marks.
Term
Meaning
Example
Common slip
Row 1 column 1
Row 1 column 2
34×25\frac{3}{4} \times \frac{2}{5}
Row 1 column 4
Row 2 column 1
Row 2 column 2
×10\times 10 moves every digit one column left
Row 2 column 4

Learning

3 boxes
3 steps

How to work with compound measures

Practise the routine version until it is automatic, then move to the multi-step questions.
Worth knowing: x2+5x+6=0x^2 + 5x + 6 = 0.
  1. Read the question and write down what is being asked for.
  2. Set out the working for compound measures in the order the method gives.
  3. Substitute the values and simplify.
  4. Check the answer against an estimate before writing it down.
Start from the definition and substitute the numbers the question gives you.
Simplify one line at a time: 34×25\frac{3}{4} \times \frac{2}{5}.
Answer: ×10\times 10 moves every digit one column left
3 rules

Key facts: Compound measures

Sketch the shape even when the question does not ask for one — it makes the next step obvious.
The layout below is the one the mark scheme expects.

Diagram showing compound measures laid out step by step

The same idea drawn out, so the method is visible.

  • Rule 1

    How compound measures behaves in the 1st of the cases the specification names.
    ×10\times 10 moves every digit one column left

  • Rule 2

    How compound measures behaves in the 2nd of the cases the specification names.
    x2+5x+6=0x^2 + 5x + 6 = 0

  • Rule 3

    How compound measures behaves in the 3rd of the cases the specification names.
    34×25\frac{3}{4} \times \frac{2}{5}
5 steps

How to work with compound measures

This idea appears again in the higher-mark questions, so it is worth over-learning.
The layout below is the one the mark scheme expects.

Diagram showing compound measures laid out step by step

The same idea drawn out, so the method is visible.
  1. Read the question and write down what is being asked for.
  2. Set out the working for compound measures in the order the method gives.
  3. Substitute the values and simplify.
Start from the definition and substitute the numbers the question gives you.
Simplify one line at a time: x2+5x+6=0x^2 + 5x + 6 = 0.
Answer: x2+5x+6=0x^2 + 5x + 6 = 0

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Examples

2 boxes
3 marks · worked

Worked example: compound measures

Sketch the shape even when the question does not ask for one — it makes the next step obvious.
The layout below is the one the mark scheme expects.

Diagram showing compound measures laid out step by step

The same idea drawn out, so the method is visible.
Worth knowing: ×10\times 10 moves every digit one column left.
4 marks · worked

Practice question 7: 34×25\frac{3}{4} \times \frac{2}{5}

Check the answer against an estimate before you move on, so a place-value slip is caught here.
Worth knowing: 34×25\frac{3}{4} \times \frac{2}{5}.

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Common questions

How many marks is compound measures usually worth?
Between one and four, depending on how many steps the question asks for.
Is this on the A Level History OCR paper?
Yes — it sits in the Ecosystems strand.