Suppose Ruth Ann has 3 routes she can choose from to get from 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?

60
60

9
9

25
25

15

Question

Suppose Ruth Ann has 3 routes she can choose from to get from 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?

60
60

9
9

25
25

15

Mercury · Answer

to get to the school to home, she needs to take 1 route from the school to the library, and 1 route from the library to her home

use the fundamental counting principle:

total # of combinations: (# of routes from school to library) * (# of routes from library to home) = ?