art supplies greatest common factor

Question

To celebrate a grand opening, the owner of an art supplies store is making free gift bags for customers. The owner has 225 pastel crayons, 75 painbrushes, and 120 tubes of oil paint. Each gift bag must be identical. What is the greatest number of gift bags the owner can make?

Answer 1

75/15 = 5

225/15 = 15

120/15 = 8

15 bags, each with 5 paintbrushes, 15 pastel crayons, and 8 tubes of oil paint

I did this by inspection, but, I can't really type this, but, if you factor each number down to prime factors, then you can circle common factors. You'll find that each number yields 5 and 3 as common prime factors. 5 x 3 = 15.