Pariksha SaathiQuantitative Aptitude
Average: Practice Questions with Answers
14 practice questions on Average, with answers; most also have an explanation or a worked solution. Try each one before you open its answer.
Read the lesson on this topic →
-
Q.1
Find the average of all natural numbers from 15 to 25, inclusive.
Show answer
Answer: 20
Solution:
- This is a consecutive (evenly spaced) sequence, so average = (first + last) / 2.
- = (15 + 25) / 2
- = 20
-
Q.2
Find the average of 198, 203, 207, 196, and 201 using the deviation method.
Show answer
Answer: 201
Solution:
- Pick base = 200. Deviations from 200: −2, +3, +7, −4, +1.
- Sum of deviations = −2 + 3 + 7 − 4 + 1 = 5. Average deviation = 5 / 5 = 1.
- Average = base + average deviation = 200 + 1 = 201.
- Check by direct addition: 198+203+207+196+201 = 1,005; 1,005/5 = 201. Matches.
-
Q.3
The average weight of 30 students in a class is 42 kg. When the teacher’s weight is included, the average rises by 1 kg. Find the teacher’s weight.
Show answer
Answer: 73 kg
Solution:
- Old sum (30 students) = 30 × 42 = 1,260 kg
- New average (31 people) = 42 + 1 = 43 kg, so new sum = 31 × 43 = 1,333 kg
- Teacher’s weight = new sum − old sum = 1,333 − 1,260 = 73 kg
-
Q.4
Find the average of 12, 15, 18, 21, and 24.
Show answer
Answer: 18
Solution:
- Sum = 12 + 15 + 18 + 21 + 24 = 90
- Average = Sum / Count = 90 / 5
- = 18
-
Q.5
Section A has 20 students with an average score of 60, and Section B has 30 students with an average score of 70. Find the combined average for both sections.
Show answer
Answer: 66
Solution:
- The section sizes differ, so the combined average is NOT the simple average (60+70)/2 = 65 — it must be weighted by the number of students.
- Total marks = (20 × 60) + (30 × 70) = 1,200 + 2,100 = 3,300
- Total students = 20 + 30 = 50
- Combined average = 3,300 / 50 = 66
-
Q.6
In a class of 40 students, the average marks are 60. There are 20 boys and 20 girls in the class. If the boys’ average marks are 50, find the girls’ average marks.
Show answer
Answer: 70
Solution:
- Total marks (40 students) = 40 × 60 = 2,400
- Boys’ total marks (20 boys) = 20 × 50 = 1,000
- Girls’ total marks = 2,400 − 1,000 = 1,400, so girls’ average = 1,400 / 20 = 70
-
Q.7
The average of 5 numbers is 27. If one number is excluded, the average of the remaining 4 numbers becomes 25. Find the excluded number.
Show answer
Answer: 35
Solution:
- Sum of all 5 numbers = 5 × 27 = 135
- Sum of the remaining 4 numbers = 4 × 25 = 100
- Excluded number = 135 − 100 = 35
-
Q.8
The average age of 6 people in a room is 30 years. A seventh person enters and the average becomes 32 years. Find the age of the seventh person.
-
Q.9
Find the average of 8, 12, 16, 20, and 24.
-
Q.10
The average marks of a class of 35 students is 72. The average of the first 20 students is 75. Find the average of the remaining 15 students.
Show answer
Answer: 68. Total = 35×72 = 2,520; first 20 total = 20×75 = 1,500; remaining total = 1,020; 1,020/15.
-
Q.11
Find the average of 505, 498, 510, 497, and 500 using the deviation method (base 500).
Show answer
Answer: 502. Deviations: +5, −2, +10, −3, 0; sum = 10; average deviation = 2; 500 + 2.
-
Q.12
Find the average of all integers from 21 to 29, inclusive.
-
Q.13
A cricketer has an average of 40 runs over 10 innings. How many runs must he score in the 11th innings to raise his average to 42?
Show answer
Answer: 62 runs. New sum needed = 11×42 = 462; old sum = 10×40 = 400; difference = 62.
-
Q.14
Section X has 15 students with an average score of 80, and Section Y has 25 students with an average score of 68. Find the combined average.
Show answer
Answer: 72.5. Total marks = 15×80 + 25×68 = 2,900; total students = 40; 2,900/40.
How these questions were made
Written by Mahesh Srivastava, Founder of Pariksha Saathi. Published: 2026-10-01.