WAEC 2021 Mathematics · Question 32
Find, correct to two decimal, the mean of 1, 2, 3, 4, and 5.
Options
- A.3.71
- B.3.70
- C.3.69
- D.3.72
Answer: A. 3.71
Explanation written with AI and checked against the answer key
Analyze the question: We need the mean of five mixed numbers, given to 2 decimal places.
Concept: Mean = (sum of values) ÷ (number of values).
Solution:
Separate the whole numbers and the fractions.
Whole numbers: 1 + 2 + 3 + 4 + 5 = 15
Fractions: 1/2 + 2/3 + 3/4 + 4/5 + 5/6
The LCM of 2, 3, 4, 5, 6 is 60:
- 1/2 = 30/60
- 2/3 = 40/60
- 3/4 = 45/60
- 4/5 = 48/60
- 5/6 = 50/60
Sum of fractions = (30 + 40 + 45 + 48 + 50)/60 = 213/60 = 3.55
Total sum = 15 + 3.55 = 18.55
Mean = 18.55 ÷ 5 = 3.71
Answer: The mean is 3.71, which is option A.
Tip: With mixed numbers, add the whole parts and the fractional parts separately. This keeps the working simple and reduces errors. Always divide by the number of items, which is 5 here.
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