How to find number of prime numbers between 1 and 100
Answers
25 prime numbers are there in between 1 and 100.
2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97…………
Finding all prime numbers between 1 and 100 in a simple way
1.First arrange numbers in a table like shown in figure.
2.Enter 6 numbers in each row until the last number (in this it is 100) reaches.
3.First we select a number and we strike off all the numbers divisible by that number.
4.Start with 2 which is greater than 1.
5.Round off number 2 and strike off entire column until the end.
6.Similarly strike off 4th column and 6th column as they are divisible by 2.
7.Now round off next number 3 and strike off entire column until end.
8.4 is gone.
9.Now round off next number 5 and strike off numbers in inclined fashion as shown in figure (they are divisible by 5). When striking off ends in some row, start again striking off with number in another end which is divisible by 5. new striking off line should be parallel to previous strike off line as shown in figure.
10.6 is gone.
11.Now round off number 7 and strike off numbers as we did in case of number 5.
8,9,10 are gone.
12.Stop at this point. Wonder why do we need to stop??
13.We have to do this procedure until we reach square root of bigger number in our numbers. (in this case square root of 100 is 10)
This technique was developed in 3rd century B.C.
A pic is mentioned in the above points....And that pic is below in attachment.
But simply to find if a no. Is prime no. Or not the thing u have to Check is ....The no. Should not be multiple of any no. Except 1 and itself.
Hope it helps u....
