4MA1/2HR Jan 2021, Question 10: Estimating the Mean for Grouped Data
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2HR (Higher) · Calculator · 4 marks
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The question, in short
Using a grouped frequency table with unknown frequency x in the 0 < d ≤ 2 class, and a given estimated mean of 4.25 km, find x and show working.
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Solution · 4 marks
- 1Use midpoints 1, 3, 5, 7, 9; the total number of students is x + 30
- 2Sum of midpoint × frequency = x + 33 + 40 + 42 + 45 = x + 160
- 3Mean: (x + 160) ÷ (x + 30) = 4.25, so x + 160 = 4.25x + 127.5
- 432.5 = 3.25x, so x = 10
Answer10
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