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

The average marks of a class of 50 students were calculated to be 64.15. It was later discovered that the marks of a student were taken to be 39, instead of 75. Find the real average of the class.

  1. 64.87

  2. 65.07

  3. 64.89

  4. 64.99

  5. 64.97
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 By taking 75 instead of 39, total increment is 36. These 36 marks are equally distributed in all 50 students. Hence. marks of each student are increased by 0.72. Hence, average becomes 64.15 + 0.72 = 64.87.

Multiple choice

A total of 19 persons went to a hotel for a combined dinner party. 13 of them spent Rs. 79 each on their dinner and the rest spent Rs. 4 more than the average expenditure of all the 19. What was the total amount of money spent by them?

  1. 94

  2. 90

  3. 84

  4. None of these

  5. 87
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let us assume that the average of all 19 persons is X. So, the total expenditure of 13 members is 13 * 79 and the rest of the people is 6(X + 4). As per the equation: 19X = 13 * 79 + 6(X + 4) => X = 1051/13 = 80.84 (approx). So, option 4 is correct.

Multiple choice

The average of 7 results is 16, the average of the first three is 14 and that of the last three is 18. What is the fourth result?

  1. 16

  2. 48
    • 16
    • 8.4

  5. 6.8
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If the average of 7 numbers is 16, then the sum of numbers must be,  112. If average of first 3 numbers is 14, then the sum of numbers must be 42. And if the average of the next 3 numbers is 18, the sum of numbers must be 54. Now, 112 - 42 - 54 = 16. Hence, the last number is 16.

Multiple choice

In a set of three numbers, the average of the first two numbers is 4, the average of the last two numbers is 5, and the average of the first and the last numbers is 6. What is the average of three numbers?

  1. 30

  2. 5

  3. 15

  4. 3

  5. 2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 Suppose the 3 numbers are A, B and C, so A + B = 2 x 4 = 8 ----------------- (1) B + C = 2 x 5 = 10 --------------- (2) A + C = 2 x 6 = 12 --------------- (3) On adding (1), (2) and (3), we get A + B + C = 15. Therefore, average = 15/3 = 5 

Multiple choice

The average of marks obtained by 125 candidates in a certain examination is 40. If the average marks of passed candidates is 40 and that of the failed candidates is 20, what is the number of candidates who passed the examination?

  1. 90

  2. 85

  3. 125

  4. 120

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

 Let the number of passed candidates be x.Then, total marks = 125 x 40 = 40x + (125 – x) x 20 = 5000 = 40x + 2500 – 20x = 20x = 2500Therefore, x = 125