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 4 of 11.

Hariharan said:   1 decade ago
Hi, santhosh.

Please explain your formula with an example.

Raji said:   1 decade ago
Hi, i would like to share with a example

to find 31 prime or not

by the above formula it can be written as 6*6>=31(p)

now upto 6 the prime nos are 2,3,5,7

31 is not divisble by any of these no,

hence it would be a prime no

Vengala rao said:   1 decade ago
Hai, santhosh your explanation is very nice.

Santhosh said:   1 decade ago
How you will consider 7 when you are checking for 31?

Karthick said:   1 decade ago
Thank you santhose:) your idea is too good to identify the prime no.

Yogendra said:   1 decade ago
Thanks santosh very much

Manali said:   1 decade ago
Thank you santosh.

R.DEIVASIGAMANI said:   1 decade ago
How to identify prime number and not prime number by easy method?

Santosh(pydah) said:   1 decade ago
91 is divided by 7 thats why it is not prime number.

Shekhar said:   1 decade ago
The number which is only divisible by itself and by 1, is called a prime number.


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