Example 1
The average age of 9 people is 21 years. When one more person joins, the average rises by 1 year. What is the age of the new person?
Answer: A) 31 years
New total = 10 × 22 = 220; old total = 9 × 21 = 189; new person = 31 years.
Averages questions for competitive exams: rules, worked examples and practice
An average is the total divided by the count. Most average questions are solved by working with totals, not averages.
Key rules and formulas
- Average = sum ÷ number of items; sum = average × number.
- If one item is added, new total = old total + new item.
- When every value rises by k, the average rises by k.
- Average of consecutive numbers = (first + last) ÷ 2.
Common traps
- Averaging two averages when the group sizes differ.
- Forgetting to update the count when someone joins or leaves.
Where Averages is asked
- IBPS Clerk Prelims (Numerical Ability)
- IBPS PO Prelims (Quantitative Aptitude)
- RRB Group D (Mathematics)
- RRB NTPC CBT 1 (Mathematics)
- SBI Clerk Prelims (Numerical Ability)
- SBI PO Prelims (Quantitative Aptitude)
- SSC CGL Tier 1 (Quantitative Aptitude)
- SSC CGL Tier 2 (Mathematical Abilities)
- SSC CHSL Tier 1 (Quantitative Aptitude)
Worked examples
Example 2
The average age of 6 people is 55 years. When one more person joins, the average rises by 2 years. What is the age of the new person?
Answer: A) 69 years
New total = 7 × 57 = 399; old total = 6 × 55 = 330; new person = 69 years.
Example 3
The average age of 8 people is 20 years. When one more person joins, the average rises by 1 year. What is the age of the new person?
Answer: D) 29 years
New total = 9 × 21 = 189; old total = 8 × 20 = 160; new person = 29 years.
More Averages practice questions
- The average age of 7 people is 52 years. When one more person joins, the average rises by 1 year. What is the age of the new person?
- The average age of 6 people is 49 years. When one more person joins, the average rises by 3 years. What is the age of the new person?
- The average age of 7 people is 62 years. When one more person joins, the average rises by 3 years. What is the age of the new person?
Frequently asked questions
What is Averages in competitive exams?
An average is the total divided by the count. Most average questions are solved by working with totals, not averages.
Which exams ask Averages questions?
On MockBazaar, Averages questions appear in IBPS Clerk Prelims, IBPS PO Prelims, RRB Group D, RRB NTPC CBT 1, SBI Clerk Prelims, SBI PO Prelims, SSC CGL Tier 1, SSC CGL Tier 2, SSC CHSL Tier 1.
What is the most common mistake in Averages?
Averaging two averages when the group sizes differ.