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The difference between the mean of the first eight composite natural numbers and the mean of the first eight prime numbers, is:
1. 1/4
2. 3/20
3. 1/5
4. 1/8

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Correct Answer - Option 4 : 1/8

Concept:

Composite Numbers = They are those numbers that have more than two factors. For example, 6 (1 × 2 × 3) is a composite number since it has three factors.

Prime Numbers = They are natural numbers greater than 1 and are not a product of two smaller natural numbers. A prime number has exactly two factors, that is, 1 and the number itself.

Formula used:

Mean/ Average = Sum of all observations/ Total no of all observations

Calculation:

First eight composite natural numbers = 4, 6, 8, 9, 10, 12, 14, 15

First eight prime numbers = 2, 3, 5, 7, 11, 13, 17, 19

Mean of the first 8 composite numbers = (4 + 6 + 8 + 9 + 10 + 12 + 14 + 15) ÷ 8 

⇒ 78 ÷ 8

Mean of the first 8 prime numbers = (2 + 3 + 5 + 7 + 11 + 13 + 17 + 19) ÷ 8  = 77 ÷ 8

∴ The required difference = 78 ÷ 8 - 77 ÷ 8 = 1/8

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