Quantitative Aptitude

Averages

1,527 Questions
All Basic average and reverse calculation 405 Adding or removing an observation 342 Weighted and combined averages 320 Replacement and correction of a recorded value 233 Ratio shortcut for two-group mixtures 111 Equal-distance average speed 59 Age, score, weight, and spending applications 32 Consecutive terms and arithmetic progressions 25

Averages Questions

Multiple choice general knowledge math & puzzles

The average age of 10 members of a committee is the same as it was 4 years ago, because an old member has been replaced by a young member. Find how much younger is the new member?

  1. 44

  2. 40

  3. 24

  4. 80
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For 10 members, the total age increased by 10 × 4 = 40 years over 4 years. Since the average remained the same, the new member must be 40 years younger than the old member to compensate for this 40-year increase. The answer is 40 years.

Multiple choice general knowledge math & puzzles

In a recent examination a class had an average score of 71. Average score of boys is 60 and average score of girls was 80. Which of the following is greater ? Col A: No. of boys who took the test Col B: No. of girls who took the test

  1. Col A

  2. Col B

  3. Both are equal

  4. Can’t be determined
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using the weighted average formula, the ratio of boys to girls is (80-71)/(71-60) = 9/11. Since the ratio is 9:11, there are more girls than boys. Therefore, Col B is greater than Col A.

Multiple choice general knowledge math & puzzles

When a student weighing 45 kgs left a class, the average weight of remaining 59 students increased by 200 g. What is the average weight of remaining 59 students?

  1. 56.8

  2. 58.2

  3. 52.2

  4. 57
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let original average = x kg for 60 students. Total weight = 60x. When 45 kg student leaves, remaining 59 students have average (x + 0.2) kg. Their total = 59(x+0.2) = 59x + 11.8. Also, 59x + 11.8 = 60x - 45 (subtracting the student who left). Thus: 11.8 + 45 = x → x = 56.8. New average = 56.8 + 0.2 = 57 kg.

Multiple choice general knowledge math & puzzles

The average weight of 10 men is increased by 1.5Kg when one of the men,who weighs 68kg is replaced by a new man.Find the weight of new man

  1. 82

  2. 83

  3. 81

  4. 80
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The total weight increase for 10 men is $10 \times 1.5 = 15$ kg. Since the new man replaced a man weighing 68 kg, his weight must be $68 + 15 = 83$ kg. Options like 82 or 81 do not account for the total weight shift correctly.

Multiple choice general knowledge math & puzzles

The average age of 20 boys in a class is 14. If the teacher is included in the group and one boy is excluded from the group, the average increases by 0.5. What is the difference in the age of the teacher & the out going student

  1. 41

  2. 45

  3. 32

  4. 20

  5. None of these
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Total age of 20 boys = 280. New group (19 boys + 1 teacher) average is 14.5. Total new age = 20 * 14.5 = 290. (Teacher - Boy) = 290 - 280 + (Boy - Boy) = 10? No, (Sum - Boy + Teacher)/20 = 14.5 => 280 - B + T = 290 => T - B = 10. None of the numerical options match.

Multiple choice general knowledge math & puzzles

The average weight of a group of 30 friends increases by 1 kg when the weight of their football coach was added. If average weight of the group after including the weight of the football coach is 31kgs, what is the weight of their football coach in kgs?

  1. 31

  2. 61

  3. 60

  4. 62

  5. 91
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let the original sum of 30 friends' weights be S. The new average after adding the coach is 31 kg for 31 people, so total weight = 31 × 31 = 961 kg. The average increased by 1 kg, so original average was 30 kg, giving S = 30 × 30 = 900 kg. Coach's weight = 961 - 900 = 61 kg. Option B is correct. Option C (60) ignores that the coach raises the average by 1 kg for 31 people.

Multiple choice general knowledge math & puzzles

Teacher: You appeared for quizzes in 4 subjects, and your average marks in them were 81. Student: How did I fare in English? Teacher: Well, your average in English Language and English Literature is 77. Student: So, how was my performance in the remaining subjects? Teacher: I am sure you can figure that out for yourself. Can you help the student find his average marks in the remaining subjects?

  1. 95

  2. 75

  3. 85

  4. 65
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total marks for 4 subjects = 4 * 81 = 324. Total marks for 2 English subjects = 2 * 77 = 154. Marks for remaining 2 subjects = 324 - 154 = 170. Average for remaining subjects = 170 / 2 = 85.

Multiple choice general knowledge math & puzzles

After replacing an old man by a new man,average of five members team of a club is same as it was 3 years ago. What is the difference between the age of the replaced one and the new member:

  1. 4

  2. 10

  3. 8

  4. 15
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For 5 team members, if 4 aged 3 years (total +12), the new member must be 15 years younger than the old member to keep the average the same as 3 years ago (compensating for all 5 members aging 3 years = 15 years total).

Multiple choice general knowledge math & puzzles

The avg. age of 30 boys of a class is 14 years. When the age of the class teacher is included, the average becomes 15 years. Find the age of class teacher?

  1. 40

  2. 39

  3. 45

  4. 42
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total age of 30 boys = 30 × 14 = 420 years. When teacher is included, 31 people have average 15, so total = 31 × 15 = 465 years. Teacher's age = 465 - 420 = 45 years. This is a standard average problem where you work backwards from totals.

Multiple choice general knowledge math & puzzles

If a boy goes school at 6.8 km/hr and returns home at 4.2 km/hr,find his average speed

  1. 4.9

  2. 5.2

  3. 4.19

  4. 5.19
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When traveling equal distances at different speeds, the average speed is the harmonic mean, not the arithmetic mean. For two speeds, average speed = 2ab/(a+b) = 2(6.8)(4.2)/(6.8+4.2) = 57.12/11 = 5.19 km/hr. Option C (4.19) is the arithmetic mean, which is incorrect for this scenario.