1.

Which of the following is NOT a prime number?1). 612). 713). 694). 67

Answer»

Prime number: A natural number LARGER than unity is a prime number if it does not have other divisors except for itself and unity.

As PROPERTIES of prime number (p):

p > 3, p2 - 1 is COMPLETELY DIVISIBLE by 24.

From options:

1) 61

⇒ (612 - 1)/24 = (3721 - 1)/24 = 155

2) 71

⇒ (712 - 1)/24 = (5041 - 1)/24 = 210

3) 69

⇒ (692 - 1)/24 = (4761 - 1)/24 = 198.33

4) 67

⇒ (672 - 1)/24 = (4489 - 1)/24 = 187

∴ From above calculation 69 is not a prime number as it does not satisfy prime number properties.


Discussion

No Comment Found