Year 10 GCSE Maths > Ratio, Proportion, Rates > Chapter 6

Proportionality graphs (y = kx, y = k/x, y = kx²)

Foundation (Grades 1-5) Non-Calculator Chapter 6/15

What You'll Learn

This chapter covers proportionality graphs (y = kx, y = k/x, y = kx²) as part of the GCSE Mathematics specification. You'll develop essential skills for Foundation tier (Grades 1-5) examination.

Why This Matters for GCSE

Exam Coverage: This topic appears in GCSE non-calculator Paper 1 and calculator Papers 2 & 3. Understanding proportionality graphs (y = kx, y = k/x, y = kx²) is essential for:

  • Answering direct GCSE exam questions on this topic
  • Problem-solving across multiple mathematics topics
  • Achieving Grades 1-5 on Foundation tier papers
  • Building mathematical reasoning and proof skills

GCSE Command Words: "Calculate", "Show that", "Prove", "Explain", "Hence"

Key Concepts

Understanding proportionality graphs (y = kx, y = k/x, y = kx²) requires mastery of these fundamental concepts:

Key Formula/Method

Apply the appropriate mathematical technique

Follow the step-by-step method shown in examples

Step-by-Step Method

Step 1: Read the question carefully and identify what's being asked
Step 2: Write down the formula or method you'll use
Step 3: Substitute values and calculate step-by-step
Step 4: Check your answer makes sense and write your final answer clearly

Worked Examples

Example 1: Foundation Tier Question

Calculate: [Question relating to proportionality graphs (y = kx, y = k/x, y = kx²)]

Identify the given information
Select the appropriate method or formula
Work through the calculation systematically
State the final answer with correct units
Answer: [Complete solution]
Mark Scheme: 1 mark for method, 1 mark for correct working, 1 mark for answer
Example 2: Multi-Step Problem

Problem: A GCSE-style problem involving proportionality graphs (y = kx, y = k/x, y = kx²)

Break down the problem into manageable steps
Apply the mathematical concepts systematically
Show all working clearly for full marks
Check the answer is reasonable
Answer: [Complete solution with units/context]
Mark Scheme: 2 marks for method, 1 mark for accuracy, 1 mark for final answer (4 marks total)

Practice Questions

Answer these GCSE-style questions. Type your answer and click "Check Answer".

1 [2 marks]

Question 1: [GCSE question on proportionality graphs (y = kx, y = k/x, y = kx²)]

2 [2 marks]

Question 2: [GCSE question on proportionality graphs (y = kx, y = k/x, y = kx²)]

3 [3 marks]

Question 3: [Multi-step GCSE question]

4 [2 marks]

Question 4: [GCSE question on proportionality graphs (y = kx, y = k/x, y = kx²)]

5 [3 marks]

Question 5: [Problem-solving question]

6 [2 marks]

Question 6: [GCSE question on proportionality graphs (y = kx, y = k/x, y = kx²)]

7 [3 marks]

Question 7: [Application question]

8 [2 marks]

Question 8: [GCSE question on proportionality graphs (y = kx, y = k/x, y = kx²)]

9 [4 marks]

Question 9: [Complex problem-solving question]

10 [3 marks]

Question 10: [Calculate question]

Common GCSE Mistakes

❌ WRONG: Common mistake related to proportionality graphs (y = kx, y = k/x, y = kx²)
✅ CORRECT: The correct approach and why it works
❌ WRONG: Another typical error students make
✅ CORRECT: The right method with clear explanation
❌ WRONG: Forgetting to show working in 'show that' questions
✅ CORRECT: Always write every step clearly for full marks

GCSE Exam Tips

  • Read carefully: Make sure you understand what the question is asking before you start
  • Show your working: Even if you know the answer, write down the steps for method marks
  • Check units: Always include units in your final answer if the question involves measurements
  • 'Show that' questions: You must prove the given answer by showing complete working
  • Time management: Don't spend too long on one question - move on and come back if needed
  • Check answers: Use the last few minutes to check your answers make sense
  • Grade boundaries: Grade 5 = strong pass, Grade 4 = standard pass - know your target!

Learning Outcomes

By the end of this chapter, you should be able to: