Multiple choice

Five years ago, the average age of A and B was 15 years. Today, the average age of A, B and C is 20 years. How old will C be after 10 years?

  1. 35 years

  2. 40 years

  3. 30 years

  4. 50 years
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

5 years ago, sum of A+B = 30. Today, sum of A+B = 30 + 10 = 40. Today, A+B+C = 20 * 3 = 60. So C = 60 - 40 = 20. After 10 years, C will be 30.

AI explanation

Today, the average age of A and B is 20 years, meaning their combined current age is 40 years. Five years ago, their combined age was 15 * 2 = 30 years, which perfectly aligns. Since the current average age of A, B, and C is 20 years, their total current age is 3 * 20 = 60 years. C's current age is the total age of all three minus the combined age of A and B, which is 60 - 40 = 20 years. Therefore, after 10 years, C will be 20 + 10 = 30 years old.

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