2. Which number is prime?
(Points : 4)
91
53
27
14

Question

2.  Which number is prime?
 (Points : 4)  
       91
        53
        27
        14

anonymous · Answer

Do you know the definition for prime numbers?

anonymous · Answer

yes

anonymous · Answer

Okay, so which number can you eliminate immediately?

anonymous · Answer

is the answer 14

anonymous · Answer

Is 14 divisible by anything *other* than 1 and itself?

anonymous · Answer

yes

anonymous · Answer

I should say, "evenly divisible" (meaning when you divide, you get a whole number with no remainder)

So yes, 14 is evenly divisible by 2 and also by 7
(14/2 = 7,    14/7 = 2)

anonymous · Answer

So we can eliminate 14 as a possible answer.

anonymous · Answer

A quick tip, any even number (a number ending in 0, 2, 4, 6, or 8) is not a prime number, because it is divisible by 2.

anonymous · Answer

So, let's look at 27 next. Do you know of anything that 27 is evenly divided by?

anonymous · Answer

3

anonymous · Answer

Exactly.
27/3 = 9

anonymous · Answer

So 27 is not a prime number.

anonymous · Answer

What about 53 and 91?

freckles · Answer

2 is actually the only even prime

anonymous · Answer

That's true, 2 is evenly divisible by itself and 1, but by nothing else, making it the only even prime number.

anonymous · Answer

So what about 53 .... is 53 evenly divisible by anything?

anonymous · Answer

no

anonymous · Answer

You are correct, 53 is the prime number.

anonymous · Answer

91 is divisible by 7,   91/7 = 13.

anonymous · Answer

For future reference, this webpage may help you: http://www.mathgoodies.com/lessons/vol3/divisibility.html