Ages with time shift: Five years ago, the average age of A, B, C, and D was 45 years. Including P now, the present average age of all five is 49 years. Find the present age of P.
Aptitude
Average
Difficulty: Medium
Choose an option
Answer
Correct Answer: 45 years
Explanation
Introduction / Context:When an average is given for a past time, we can update totals by adding years for each person to obtain present totals.Given Data / Assumptions:
- Five years ago: average of A, B, C, D = 45 years
- Now: average of A, B, C, D, P = 49 years
Concept / Approach:Compute past total of four, add 5 years per person to get present total of the four, then find P from the five person total.Step-by-Step Solution:
Past total (four) = 4 * 45 = 180Present total (same four) = 180 + 4 * 5 = 200Present total (five) = 5 * 49 = 245P present age = 245 - 200 = 45 yearsVerification / Alternative check:Average check holds with computed values.Why Other Options Are Wrong:
- 64, 48, 40 years: Do not equal the difference between the five person present total and the updated four person present total.
Common Pitfalls:Forgetting to add 5 years for each of the four when moving from past to present totals.Final Answer:
45 years