Aptitude - Numbers - Discussion

Discussion Forum : Numbers - General Questions (Q.No. 1)
1.
Which one of the following is not a prime number?
31
61
71
91
Answer: Option
Explanation:
91 is divisible by 7. So, it is not a prime number.
Discussion:
107 comments Page 6 of 11.

Priyanka.c(IT) said:   1 decade ago
Prime number is defined as divisible by "itself" and by "one" only.

Balu said:   1 decade ago
Hi,

11>square root of(91).
(11*11=121 =>11^2 > square root of (91)).

Then prime numbers below 11 are 2, 3, 5, 7

So 91 is divisible by 7.
Hence 91 is not a prime number.

Kishor said:   1 decade ago
Prime number means, the number which is non actionable.

Karthik said:   1 decade ago
Number is 91.
Take out last 1 and multiply by 2.

9 - (1*2) = 9 - 2 = 7.
So it is divisible by 7.

If we have more digits repeat the process.
It is easy.

Unaisvatts said:   1 decade ago
@KARTHIK.

If number is 97.

9-(2*7) = is not positive number.

Kaviya said:   1 decade ago
Which number is only divisible by 1 and the same number is called prime number.

Shaziya said:   1 decade ago
A negative number can be a prime number?

Tinku das said:   1 decade ago
I want to know why 1 is not prime no?

Manju gouda said:   1 decade ago
Basically a number is prime no. If it has exactly 2 distinct factors. For e.g for 13 factors are 13 and 1. So it is a prime number. But for 1 factors are 1 only. So it is not a prime number.

Kavitha said:   1 decade ago
Please, give me detailed explanation about the prime number and solve the steps one by one in the problem.


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