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0580/33 May/Jun 2025, Question 19: Reciprocal Functions

Cambridge IGCSE Mathematics 0580 · Paper 33 (Core) · Calculator · 6 marks

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The question, in short

Complete a table for y = 20/x, plot the curve for 1 ≤ x ≤ 5, then use the graph to solve 20/x = 8.

Summarised in our own words. Use the official paper for the exact wording and the diagram.

Part (a) · 2 marks

Fill in the two missing y-values in the table for y = 20/x at x = 3 and x = 4.

  1. 1x = 3: y = 20/3 = 6.666… ≈ 6.67
  2. 2x = 4: y = 20/4 = 5

Answer| x | 1 | 2 | 3 | 4 | 5 | | y | 20 | 10 | 6.67 | 5 | 4 |

Part (b) · 3 marks

Draw the graph of y = 20/x on the grid for x from 1 to 5.

  1. 1Plot (1, 20), (2, 10), (3, 6.67), (4, 5), (5, 4)
  2. 2Join the points with a smooth curve from x = 1 to x = 5

AnswerCorrect graph

Part (c) · 1 mark

Use your graph to find the x-value where 20/x equals 8.

  1. 1Draw the line y = 8 and read off x where it meets the curve
  2. 220/x = 8 gives x = 20 ÷ 8 = 2.5

Answer2.45 to 2.55

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Also searched as: 0580/33/M/J/25 · 0580_s25_qp_33 · 0580 s25 33 · question 19.
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