WAEC 2021 Mathematics · Question 32

Find, correct to two decimal, the mean of 112\frac{1}{2}, 223\frac{2}{3}, 334\frac{3}{4}, 445\frac{4}{5}, and 556\frac{5}{6}.

Options

  1. A.3.71
  2. B.3.70
  3. C.3.69
  4. 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.

AI can make mistakes. Report anything that looks wrong.

Past questions © the examination body (JAMB/WAEC/NECO). DeeepSolve is not affiliated with them. Rights holders: see /copyright.