In a family of 21 people, the average age is 14years. If the age of the grandfather is not counted, the average age drops to 12 years. What is the age of the grandfather?

  • A 35 years
  • B 40 years
  • C 42 years
  • D 54 years
jamb 1989mathematics

The correct answer is C. 42 years

In a family of 21 people, the total age of all members is 21 14 = 294 years. If the age of the grandfather is not counted, there are 21 - 1 = 20 people left, and their total age is 20 12 = 240 years. Therefore, the age of the grandfather is 294 - 240 = 54 years.

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