The average age of A and B is 20 years. If A is replaced by C, the average becomes 19 years. The average age of C and A is 21 years. What are the ages of A, B and C respectively (in years)?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 22, 18, 20
Each average of two gives the sum of that pair; half the total of the three pair sums is the sum of all three ages.
A \(+\) B \(=40\), B \(+\) C \(=38\), C \(+\) A \(=42\)
A \(+\) B \(+\) C \(\displaystyle =\frac{40+38+42}{2}=60\)
A \(=60-38=22\), B \(=60-42=18\), C \(=60-40=20\)