Array puzzle

Question

I am an array made with 40 tiles. I have an odd number of rows and an even number of tiles in each of my rows. The number of of my rows plus the number of tiles in each of my rows equals 13. How many rows do I have

Answer 1

Actually, you can make guesses, realizing that the two numbers (rows and tiles/row) are FACTORS of 40.

It shouldn't be too long before the correct answer pops into your head, probably without having to write anything on paper/