Which of the following numbers is composite?

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RRB ALP CBT I 30 Aug 2018 Shift 3 Official Paper
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  1. 51
  2. 41
  3. 61
  4. 31

Answer (Detailed Solution Below)

Option 1 : 51
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Detailed Solution

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Concept used:

1. A composite number is a positive integer that can be formed by multiplying two smaller positive integers.

2. Prime numbers are natural numbers (>=2) that are divisible by only 1 and the number itself.

Calculation:

51 = 3 × 17

41 = 41 × 1

61 = 61 × 1

31 = 31 × 1

∴ Only 51 is a composite number among the options. 

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