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JAMB Mathematics 2004 Question 43

Question 43

Measures of Central Tendency

The mean age of a group of students is 15 years. When the age of a teacher, 45 years old, is added to the ages of the students, the mean of their ages becomes 18 years. Find the number of students in the group

  1. A.7
  2. B.9
  3. C.15
  4. D.42
Show the answer and explanation

Answer: B (9)

Explanation

With n students, (15n + 45)/(n + 1) = 18, so 15n + 45 = 18n + 18 and n = 9.