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JAMB Mathematics 1984 Question 48

Question 48

Data Presentation

Measurements of the diameters, in centimeters, of 20 copper spheres are distributed as shown below:
Class boundary in cm: 3.35 − 3.45, 3.45 − 3.55, 3.55 − 3.65, 3.65 − 3.75
Frequency: 3, 6, 7, 4
What is the mean diameter of the copper sphere?

  1. A.3.40cm
  2. B.3.58cm
  3. C.3.56cm
  4. D.3.62cm
  5. E.3.63cm.
Show the answer and explanation

Answer: C (3.56cm)

Explanation

Use the class mid-points 3.4, 3.5, 3.6, 3.7: Σfx = 10.2 + 21.0 + 25.2 + 14.8 = 71.2, and 71.2 ÷ 20 = 3.56cm.