Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 1)
1.
Which one of the following is not a prime number?
Answer: Option
Explanation:
91 is divisible by 7. So, it is not a prime number.
Discussion:
108 comments Page 3 of 11.
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.
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.
Kavitha said:
6 years ago
When we apply the condition.
n*n >=p for 91! How does that work?
(10*10>=91. Factors of 10 -2, 5, 10. So how is this condition satisfiying for the above question).?
n*n >=p for 91! How does that work?
(10*10>=91. Factors of 10 -2, 5, 10. So how is this condition satisfiying for the above question).?
Deekshi said:
8 years ago
Code for prime numbers below 100 is 442233322321.
2,3,5,7 (4)
11,13,17,19 (4)
23,29 (2)
31,37 (2)
41,43,47 (3)
53,59 (2)
61,67 (20
71,73,79 (3)
83,89 (2)
97 (1)
2,3,5,7 (4)
11,13,17,19 (4)
23,29 (2)
31,37 (2)
41,43,47 (3)
53,59 (2)
61,67 (20
71,73,79 (3)
83,89 (2)
97 (1)
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.
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.
Nithish said:
7 years ago
Prime number is nothing but a number divisible only by one and that number. But 91 is divisible by Seven. So it's not a prime number.
J.KRISHNAVENI said:
9 years ago
@Dilipkumar.
Only for few numbers given for short cut in prime numbers. So please given for other numbers in the short cut method.
Only for few numbers given for short cut in prime numbers. So please given for other numbers in the short cut method.
Deepika said:
9 years ago
@Nidhin.
Thank you for this shortcut. It's really helpful.
Will you tell me the shortcut to remember prime number above 100?
Thank you for this shortcut. It's really helpful.
Will you tell me the shortcut to remember prime number above 100?
Tharun said:
4 years ago
91 is correct because the prime number is one which is having two distinct factors so, that 91 having more than two factors.
(6)
Nishant said:
1 decade ago
I know that prime numbers are of the form either 6k-1 or 6K+1 . Here 91 is of the form 6k+1 but still it is prime how come?
Puneet said:
1 decade ago
@Dilipkumar(Cse).
That is an awesome way to remember all prime numbers between 1 & 100. There is a pattern too.
That is an awesome way to remember all prime numbers between 1 & 100. There is a pattern too.
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