Function model of Bao's distance

Question

bao walked away from his house at a constant speed of 3 feet per second until he was 900 feet from his house. he stopped and talked to a friend for 2 minutes, and then ran home at a constant speed of 9 feet per second.  What is the distance from his home between 300 and 420 seconds after bao left his house?

Answer 1

It takes him 900/3=300 seconds to walk 900 ft from his house. Two minutes is 120 seconds, so he is 900 feet from his house between 300 and 300+120=420 seconds since he started out. (It takes him 900/9=100 more seconds to run home, 520 seconds after leaving home.) So, between 300 and 420 seconds he is 900 feet from home.