Question
There are 30 women and 20 men at a gym. The mean height of all 50 people is 167.6 cm. The mean height of the 20 men is 182 cm. Work out the mean height of the 30 women.
Worked Solution
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Find the total height of all 50 people: 50 × 167.6 = 8380 cm.
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Find the total height of the 20 men: 20 × 182 = 3640 cm.
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The total height of the 30 women must be: 8380 – 3640 = 4740 cm.
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The mean height of the women is 4740 ÷ 30 = 158 cm.
158
A common error is to average 167.6 and 182 directly to find the women's mean — this ignores the different group sizes (30 women vs 20 men).
Assessment Objectives (question level, Edexcel 1MA1 spec — not per step)