Grade seven, Edexcel GCSE Maths

Revision Notes

What is proportion?

Proportion is a way of talking about how two variables are related to each other.

Direct Proportion: as one variable goes up the other goes up by the same Factor

eg  If one variable is multiplied by 3, so is the other

Inverse Proportion: as one variable goes up the other goes down by the same Factor

eg  If one variable is multiplied by 3, the other is divided by 3

You should know what the graphs look like:

y=kx, IGCSE & GCSE Maths revision notes
y=k/x, IGCSE & GCSE Maths revision notes

How do we deal with proportion questions?

1. Identify the two VARIABLES (called A and B below) 

2. Choose TYPE of proportion:

  • A is DIRECTLY proportional to B use formula A = kB
  • A is INVERSELY proportional to B use formula A = k÷B

3. FIND k using the values given in the question 

4. Write FORMULA for A in terms of B (using your value of k)

5. USE formula to find required quantity

Example

Direct & Inverse Proportion Example, IGCSE & GCSE Maths revision notes

Question

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Edexcel GCSE Maths Notes

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