PREVIOUSLY ASKED IN:
PSC Miscellaneous Prelims 2018
Answer
16 years
Explanation
According to the rule of averages, Total Age = Average Age × Number of Persons. Given, the average age of A, B, and C (3 persons) is 22 years. Therefore, the sum of their ages = 3 × 22 = 66 years. It is also given that the average age of B and C (2 persons) is 25 years. Therefore, the sum of their ages = 2 × 25 = 50 years. To find the age of A, we subtract the sum of B and C's ages from the sum of all three. Therefore, Age of A = 66 - 50 = 16 years.
Key Points
- > In average problems, always calculate the total sum first.
- > Sum of ages of 3 people (A+B+C) = 3 × 22 = 66.
- > Sum of ages of 2 people (B+C) = 2 × 25 = 50.
- > Age of A = Total sum of all three - Sum of B and C.
- > Age of A = 66 - 50 = 16 years.
Additional Information
Age and Average Table
| Persons | Count | Average Age | Total Sum of Ages |
|---|---|---|---|
| A, B, C | 3 | 22 | 3 × 22 = 66 |
| B, C | 2 | 25 | 2 × 25 = 50 |
| A alone | 1 | - | 66 - 50 = 16 |
Memory Tips
- Mental Deviation Trick: The group average is 22. B and C average 25, which means they are each +3 above the group average. So together they are +6. To maintain the group average of 22, person A must be -6 below the average. 22 - 6 = 16 years.