A group of 20 people has the oldest person with 90 years of age. The average…
2024202420242024
A group of 20 people has the oldest person with 90 years of age. The average of the group is reduced by 4, if the oldest person is reduced by someone new, Find the age of the new person.
- A.
80 years
- B.
60 years
- C.
30 years
- D.
10 years
Attempted by 23 students.
Show answer & explanation
Correct answer: D
Key idea: The total decrease in the sum of ages equals the number of people multiplied by the decrease in the average.
Total decrease in sum = 20 × 4 = 80 years.
New person's age = 90 − 80 = 10 years.
Check: the total decreases by 80, so the average decreases by 80/20 = 4, which matches the problem statement.
Answer: 10 years.