Average Questions Answers

• 1. Average of all prime numbers between 30 to 50

  1. 37
  2. 37.8
  3. 39
  4. 39.8

  Answer And Explanation

  Answer: Option D

  Explanation:

  Prime numbers between 30 and 50 are:
  31, 37, 41, 43, 47
  
  Average of prime numbers between 30 to 50 will be
  $$\begin{aligned} (\frac{31+37+41+43+47}{5}) = \frac{199}{5} = 39.8 \end{aligned}$$

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• 2. Reeya obtained 65, 67, 76, 82 and 85 out of 100 in different subjects, What will be the average.

  1. 70
  2. 75
  3. 80
  4. 85

  Answer And Explanation

  Answer: Option B

  Explanation:

  $$\begin{aligned} ( \frac {65+67+76+82+85}{5} ) = 75 \end{aligned}$$

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• 3. Find the sum of first 30 natural numbers

  1. 470
  2. 468
  3. 465
  4. 463

  Answer And Explanation

  Answer: Option C

  Explanation:

  Sum of n natural numbers
  $$\begin{aligned} = \frac{n(n+1)}{2} \end{aligned}$$
  
  $$\begin{aligned} = \frac{30(30+1)}{2} = \frac{30(31)}{2} = 465 \end{aligned}$$

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• 4. Find the average of first 10 multiples of 7

  1. 35.5
  2. 37.5
  3. 38.5
  4. 40.5

  Answer And Explanation

  Answer: Option C

  Explanation:

  $$\begin{aligned} = \frac {7(1+2+3+...+10)}{10} \end{aligned}$$
  
  $$\begin{aligned} = \frac {7(10(10+1))}{10 \times 2} \end{aligned}$$
  
  $$\begin{aligned} = \frac {7(110)}{10 \times 2} = 38.5 \end{aligned}$$

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• 5. The average of four consecutive odd numbers is 24. Find the largest number.

  1. 25
  2. 27
  3. 29
  4. 31

  Answer And Explanation

  Answer: Option B

  Explanation:

  Let the numbers are x, x+2, x+4, x+6, then
  $$\begin{aligned} => \frac{x+(x+2)+(x+4)+(x+6)}{4} = 24 \end{aligned}$$
  
  $$\begin{aligned} => \frac{4x+12)}{4} = 24 \end{aligned}$$
  
  $$\begin{aligned} => x+3 = 24 => x = 21 \end{aligned}$$
  
  So largest number is 21 + 6 = 27

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• 6. Average of 10 numbers is zero. At most how many numbers may be greater than zero

  1. 0
  2. 1
  3. 5
  4. 9

  Answer And Explanation

  Answer: Option D

  Explanation:

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• 7. Find the average of all numbers between 6 and 34 which are divisible by 5

  1. 15
  2. 20
  3. 25
  4. 30

  Answer And Explanation

  Answer: Option B

  Explanation:

  $$\begin{aligned} Average = (\frac{10+15+20+25+30}{5}) = \frac{100}{5} =20 \end{aligned}$$

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