How many thirds of a hallway are there to decorate in 5 hallways

15

Step-by-step explanation:

Something divided into thirds will be divided into three equal pieces.

One hall way divided into thirds would be 3, 1 * 3 = 3

two hallways divided into thirds would be 6, 2 * 3 = 6

three hallways divided into thirds would be 9, 3 * 3 = 9

four hallways divided into thirds would be 12, 4 * 3 = 12

five hallways divided into thirds would be 15, 5 * 3 = 15