Posted by Nikki on .
Which of these numbers is prime? Explain why or why not.
407
409
411
413

Math ? 
Writeacher,
http://en.wikipedia.org/wiki/Prime_number
So ... which of these can be divided evenly only by itself and 1?
?? 
Math ? 
tchrwill,
Which one(s) are evenly divisible by prime numbers less than the sqrt of the number. The square root of the largest is 20.32. Since they are all odd, 2 is not a divisor, Therefore, division by 3, 7, 11, 13, and 19 are the only tests.