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Free Averages MCQs with Answers

90 Averages MCQs from Mathematics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

An average represents the total of a set of values divided by the number of values, and a weighted average gives different importance to different groups. Problems involve missing values, combined averages, replacement of observations, and changes in the average, so the total and count must be tracked separately.

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90 questions · page 5 of 5

81. The average age of 8 men increases by 2 years when two women are included in place of two men of ages 20 and 24 years. Find the average age of the women?

  • A. 36 years
  • B. 24 years
  • C. 30 years
  • D. 18 years

Explanation: The original total age of 8 men is 8x years. The average rises by 2 years while the number remains 8, so replacing the 20-year-old and…

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Correct answer: 30 years

82. The average of first five prime numbers greater than 20 is____________?

  • A. 31.00
  • B. 31.01
  • C. 32.00
  • D. 32.2

Explanation: The first five prime numbers greater than 20 are 23, 29, 31, 37 and 41.

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Correct answer: 32.2

83. The average of 9 observations was 9, that of the 1st of 5 being 10 and that of the last 5 being 8. What was the 5th observation?

  • A. 9
  • B. 8
  • C. 7
  • D. 6Educational Resources

Explanation: The total of all 9 observations is 9 x 9 = 81, the first 5 total 5 x 10 = 50, and the last 5 total 5 x 8 = 40.

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Correct answer: 9

84. The average of 1st 3 of 4 numbers is 16 and of the last 3 are 15. If the sum of the first and the last number is 13. What is the last numbers?

  • A. 8
  • B. 6
  • C. 5
  • D. 2

Explanation: Let the four numbers be a, b, c and d. The first three sum to 3 x 16 = 48, the last three sum to 3 x 15 = 45, so d - a = -3; together with…

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Correct answer: 5

85. The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy?

  • A. 15
  • B. 9
  • C. 18
  • D. 21Quiz Mode Feature

Explanation: The three boys' total age is 3 x 15 = 45 years. Their ratio total is 3 + 5 + 7 = 15 parts, so each part represents 45/15 = 3 years; the…

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Correct answer: 9

86. The average of first 10 odd numbers is_____________?

  • A. 11
  • B. 10
  • C. 12
  • D. 17

Explanation: The first 10 odd numbers are 1 through 19. For an evenly spaced list, the average is the mean of the first and last values: (1 + 19)/2 =…

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Correct answer: 10

87. The average of first 10 natural numbers is____________?

  • A. 5
  • B. 5.5
  • C. 6.5
  • D. 6

Explanation: The first 10 natural numbers are 1 through 10, whose sum is 10 x 11/2 = 55. Dividing by 10 numbers gives an average of 55/10 = 5.5.

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Correct answer: 5.5

88. The average of first ten prime numbers which are odd is____________?

  • A. 12.9
  • B. 13.8
  • C. 15.8
  • D. 17

Explanation: The first 10 odd prime numbers are 3, 5, 7, 11, 13, 17, 19, 23, 29 and 31. Their sum is 158, so the average is 158/10 = 15.8.

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Correct answer: 15.8

89. The average of 11 numbers is 10.9. If the average of first six is 10.5 and that of the last six is 11.4 the sixth number is_____________?

  • A. 11.0
  • B. 11.3
  • C. 11.4
  • D. 11.5

Explanation: The total of all 11 numbers is 11 x 10.9 = 119.9. The first six total 6 x 10.5 = 63.0, while the last six total 6 x 11.4 = 68.4; adding…

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Correct answer: 11.5

90. The average of first 10 even numbers is___________?

  • A. 18
  • B. 22
  • C. 9
  • D. 11

Explanation: The first 10 even numbers are 2, 4, ..., 20. Since they form an arithmetic sequence, their average is (first number + last number) / 2 =…

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Correct answer: 11
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