Mrs. Evans has 13 pictures to hang on a wall. Is there any way she can arrange the pictures ib rows other than 1×13 or 13×1, so that the same number of pictures is in each row? Tell whether 13 is a composite or prime number. Explain.

A prime number is a positive integer that only has a factor of one and itself. Factors are the numbers we multiply together to get another number. 
Example: 11 is a prime number. To get 11, we can only multiply 1x11. 

A composite number is a positive integer that has factors other than one and itself. 
Example: 12 is a composite number. To get 12, you can multiply together 1x12, 2x6, and 3x4. 1, 2, 3, 4, 6, and 12 are all factors of 12. 

In the problem you are trying to solve, Mrs. Evans wants to hang 13 pictures with the same number of pictures in each row. Find all of the factors of 13: 1, 13. Those are the only numbers we can multiply together to get 13. Since its factors are only 1 and itself, 13 is a prime number. Because 13 is a prime number, there are no other possible ways she can arrange her pictures into rows with the same number of pictures in each.