On a normal day, Julia can run a mile in 10 minutes. However, today she decided to wear her new shoes to run. They were uncomfortable and slowed her mile down to 13 minutes. How much longer would it take Julia to run 5 miles in her new shoes than if she wore her old ones? Let's think first. Chain of thought:
With her regular shoes, it should take 5 * 10 = 50 minutes to run five miles. If she wore her new shoes it would take 13 * 5 = 65 minutes to run five miles. 65 - 50 = 15 more minutes.
Therefore, the answer is 15.