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Simultaneous equations

Simultaneous equations for GCSE Statistics OCR Higher: what it means, how to set the working out, and the questions it is asked in.
  • GCSE
  • OCR
  • Statistics
  • Higher
  • Spec P13 · P7 · P12
  • 13 min read
  • 6 revision boxes

Introduction

2 boxes
3 min read

What is simultaneous equations?

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Transcript

A short spoken summary of simultaneous equations and where it is used.

A spoken walk-through of simultaneous equations before you read the notes.
Practise the routine version until it is automatic, then move to the multi-step questions.
The layout below is the one the mark scheme expects.

Diagram showing simultaneous equations laid out step by step

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

The simultaneous equations reference table

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 simultaneous equations laid out step by step

The same idea drawn out, so the method is visible.
Worth knowing: x2+5x+6=0x^2 + 5x + 6 = 0.
Term
Meaning
Example
Row 1 column 1
Row 1 column 2
x2+5x+6=0x^2 + 5x + 6 = 0
Row 2 column 1
Row 2 column 2
a2+b2=c2a^2 + b^2 = c^2
Row 3 column 1
Row 3 column 2
34×25\frac{3}{4} \times \frac{2}{5}
Row 4 column 1
Row 4 column 2
×10\times 10 moves every digit one column left

Learning

2 boxes
5 steps

How to work with simultaneous equations

This idea appears again in the higher-mark questions, so it is worth over-learning.
Worth knowing: ≈160\approx 160.
  1. Read the question and write down what is being asked for.
  2. Set out the working for simultaneous equations 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: ×10\times 10 moves every digit one column left.
Answer: x2+5x+6=0x^2 + 5x + 6 = 0
3 rules

Key facts: Simultaneous equations

The examiner marks the working, so a correct answer with no method still drops marks.
Worth knowing: x2+5x+6=0x^2 + 5x + 6 = 0.

  • Rule 1

    How simultaneous equations behaves in the 1st of the cases the specification names.
    ≈160\approx 160

  • Rule 2

    How simultaneous equations behaves in the 2nd of the cases the specification names.
    a2+b2=c2a^2 + b^2 = c^2

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Examples

2 boxes
1 marks · worked

Worked example: simultaneous equations

Practise the routine version until it is automatic, then move to the multi-step questions.
The layout below is the one the mark scheme expects.

Diagram showing simultaneous equations laid out step by step

The same idea drawn out, so the method is visible.
4 marks · worked

Practice question 6: x2+5x+6=0x^2 + 5x + 6 = 0

Work through the method one line at a time and write down what changes at each step.
Worth knowing: x2+5x+6=0x^2 + 5x + 6 = 0.

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Common questions

How many marks is simultaneous equations usually worth?
Between one and four, depending on how many steps the question asks for.
Is this on the GCSE Statistics OCR Higher paper?
Yes — it sits in the Vectors strand.