Average MCQs with Answers and Explanations for Competitive Exams

Question #21

The average weight of 20 students is 50 kg. If the teacher's weight is added, the average becomes 52 kg. Find the teacher's weight.

A. 88 kg

B. 92 kg

C. 90 kg

D. 94 kg

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Correct Answer: Option B

Explanation:
Total weight of 20 = 20×50=1000. Total of 21 =21×52=1092. Teacher's weight =1092-1000=92.

This question belongs to: Maths Average

Question #22

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Find the average of all numbers from 1 to 15 that are divisible by 3.

A. 8

B. 9

C. 10

D. 12

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Correct Answer: Option B

Explanation:
Numbers: 3,6,9,12,15 sum=45, count=5, avg=9.

This question belongs to: Maths Average

Question #23

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The average of 8 numbers is 35. If each number is multiplied by 2, what is the new average?

A. 35

B. 70

C. 105

D. 17.5

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Correct Answer: Option B

Explanation:
New average = 35×2=70.

This question belongs to: Maths Average

Question #24

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The average of 10 numbers is 25. If one number is removed, the average becomes 23. What is the removed number?

A. 43

B. 38

C. 40

D. 45

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Correct Answer: Option A

Explanation:
Sum of 10 =250. Sum of 9 =9×23=207. Removed number =250-207=43.

This question belongs to: Maths Average

Question #25

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What is the average of the cubes of first 3 natural numbers?

A. 14

B. 12

C. 18

D. 10

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Correct Answer: Option B

Explanation:
Cubes:1,8,27 sum=36, avg=36/3=12.

This question belongs to: Maths Average

Question #26

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The average age of 4 boys is 16 years. If their ages are in ratio 1:2:3:4, what is the age of the oldest boy?

A. 25.6 years

B. 28

C. 24

D. 26

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Correct Answer: Option A

Explanation:
Sum =4×16=64. Ratio sum=10. Oldest = (4/10)×64 =25.6.

This question belongs to: Maths Average

Question #27

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The average of 6 numbers is 18. If one number is 30, find the average of the remaining 5.

A. 14.4

B. 16.8

C. 15.6

D. 16

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Correct Answer: Option C

Explanation:
Sum=6×18=108. Remaining sum=108-30=78. Avg=78/5=15.6.

This question belongs to: Maths Average

Question #28

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Find the average of the first 8 multiples of 4.

A. 16

B. 22

C. 20

D. 18

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Correct Answer: Option D

Explanation:
Multiples: 4,8,12,16,20,24,28,32 sum=144, count=8, avg=18.

This question belongs to: Maths Average

Question #29

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The average of 9 observations is 40. If each observation is decreased by 4, what is the new average?

A. 40

B. 44

C. 32

D. 36

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Correct Answer: Option D

Explanation:
New average =40-4=36.

This question belongs to: Maths Average

Question #30

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The average marks of a student in 5 subjects is 80. If he scores 90 in the sixth subject, what is his new average?

A. 82.5

B. 80.5

C. 81.67

D. 81.33

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Correct Answer: Option C

Explanation:
Sum of 5 =5×80=400. Sum of 6 =400+90=490. New average =490/6=81.666... ≈81.67.

This question belongs to: Maths Average

Question #31

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The average of 2 numbers is 15. If one number is 10, what is the other?

A. 20

B. 25

C. 5

D. 15

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Correct Answer: Option A

Explanation:
Sum =2×15=30. Other =30-10=20.

This question belongs to: Maths Average

Question #32

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What is the average of all odd numbers from 1 to 19?

A. 9.5

B. 10

C. 9

D. 10.5

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Correct Answer: Option B

Explanation:
Odd numbers: 1,3,5,...,19. There are 10 terms. Sum = n^2 =10^2=100. Average=100/10=10.

This question belongs to: Maths Average

Question #33

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The average of 7 numbers is 50. If each number is increased by 5, what is the new average?

A. 55

B. 50

C. 45

D. 60

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Correct Answer: Option A

Explanation:
New average =50+5=55.

This question belongs to: Maths Average

Question #34

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The average height of 5 students is 150 cm. If a new student of height 160 cm joins, what is the new average?

A. 151.67 cm

B. 151 cm

C. 155 cm

D. 152 cm

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Correct Answer: Option A

Explanation:
Sum of 5 =5×150=750. Sum of 6 =750+160=910. New average =910/6=151.67.

This question belongs to: Maths Average

Question #35

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Find the average of the first 10 even numbers.

A. 12

B. 11

C. 10

D. 11.5

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Correct Answer: Option B

Explanation:
Sum of first 10 even numbers = 10×11=110 (since sum = n(n+1) for first n evens? Actually sum = 2+4+...+20 = 2*(1+2+...+10)=2*55=110). Average=110/10=11.

This question belongs to: Maths Average

Question #36

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The average of 3 numbers is 24. If one number is 12 and another is 30, find the third.

A. 30

B. 18

C. 36

D. 24

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Correct Answer: Option A

Explanation:
Sum=3×24=72. Third =72-12-30=30.

This question belongs to: Maths Average

Question #37

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The average salary of 10 employees is Rs 5000. If a new employee joins with salary Rs 7000, what is the new average?

A. 5200

B. 5181.82

C. 5150

D. 5220

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Correct Answer: Option B

Explanation:
Total =10×5000=50000. New total =57000. New average =57000/11=5181.82.

This question belongs to: Maths Average

Question #38

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The average of 12 numbers is 15. If each number is multiplied by 2 and then 3 is added, what is the new average?

A. 33

B. 27

C. 36

D. 30

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Correct Answer: Option A

Explanation:
New average = (old average ×2)+3 = (15×2)+3=33.

This question belongs to: Maths Average

Question #39

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The average of 5 numbers is 32. If one number is excluded, the average becomes 30. Find the excluded number.

A. 36

B. 42

C. 40

D. 38

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Correct Answer: Option C

Explanation:
Sum of 5 =160. Sum of 4=4×30=120. Excluded=160-120=40.

This question belongs to: Maths Average

Question #40

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What is the average of the first 5 prime numbers?

A. 5.6

B. 5.4

C. 5.8

D. 6.0

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Correct Answer: Option A

Explanation:
Primes: 2,3,5,7,11 sum=28, avg=28/5=5.6.

This question belongs to: Maths Average

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