How do you tell if a number is prime?

Answer 1

A Prime number cannot be divided by any other number except for 1 and itself and result in a whole number (positive integer). For example, 3 is a prime number. You can divide 3 by one or three and get a whole number. If you divide three by any other positive integer (for example 2) you get a fraction (or a decimal). 10 on the other hand is NOT a prime number. 10 is divisible by 1 and 10, but it is also divisible by 5 and 2: 10/2 = 5 10/5 = 2 If a number cannot be divided by any whole number other than itself or 1, with a whole number as the result the number is prime. 1/1=1 prime 2/2=1, 2/1=2 prime 3/3=1, 3/1=3 prime 4/4=1, 4/1=4, but 4 can also be divided by 2 with a whole number as the result 4/2=2, so it is not prime. Just think if are there any two numbers that can be multiplied together to get the number other than itself and 1. If there are, it is not prime. For example 25 is not prime bexuse 5x5=25. 13 is prime because no whole numbers, other than 13 and 1, can be multiplied together to get 13. 1-prime 2-prime 3-prime 4-not prime (2x2=4) 5-prime 6-not prime (2x3=6) 7-prime 8-not prime (2x4=8) 9-not prime (3x3=9) 10-not prime (2x5=10) 11-prime 12-not prime (3x4=12, 2x6=12)