Multiple choice

The average age of 17 persons is 39 years. If the average age of the first 9 persons is 35 years, and the average age of the last 9 persons is 44 years, what is the age of the 9th person?

  1. 48 years

  2. 45 years

  3. 41 years

  4. 36 years

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total age of 17 persons = 17×39=663. Sum of first 9 = 9×35=315. Sum of last 9 = 9×44=396. The 9th person is counted in both groups. So 9th person's age = 315+396-663=48. Or: 663-315-396=-48, take absolute value.