What goes into 15 and 80?

To determine what goes into both 15 and 80, we need to find their common factors. The factors of 15 are 1, 3, 5, and 15, while the factors of 80 are 1, 2, 4, 5, 8, 10, 16, 20, 40, and 80. The only common factor between the two numbers is 1 and 5. Therefore, the numbers that go into both 15 and 80 are 1 and 5.