Suppose Ruth Ann has 3 routes she can travel between the school to the library, and 5 routes from the library to her home. How many routes are there from Ruth Ann’s school to her home with a stop at the library?
There are 3 routes from the school to the library and 5 routes from the library to her home.
Therefore, there are a total of 3 x 5 = 15 routes from Ruth Ann's school to her home with a stop at the library.