0580/21 Oct/Nov 2025, Question 13: Finding the Median and Quartiles
Cambridge IGCSE Mathematics 0580 · Paper 21 (Extended) · Non-calculator · 4 marks
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The question, in short
Ten test scores include two unknown values x, and their mean is 8. Find the interquartile range, showing all working.
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Solution · 4 marks
- 1Mean 8, so total = 10 × 8 = 80
- 29 + 8 + 9 + 10 + 7 + 9 + 9 + 7 + 2x = 80, so 68 + 2x = 80 and x = 6
- 3In order: 6, 6, 7, 7, 8, 9, 9, 9, 9, 10
- 4Lower quartile = middle of 6, 6, 7, 7, 8 = 7; upper quartile = middle of 9, 9, 9, 9, 10 = 9
- 5IQR = 9 − 7 = 2
Answer2 or 2.25 or 2.5
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