Lizzy: Stephen rides his bicycle to church. During the first third of his trip, he travels at a speed of 16 miles per hour. During the second third of his trip, riding uphill, he travels a speed of 12 miles per hour. During the last third of his trip, he rides downhill at a speed of 20 miles per hour. If each third of his trip takes 15 minutes, what is the distance Stephen rides his bicycle to church, in miles?.
Me: Hmmm, let me think. I think this is the detailed solution:
15 minutes is 15 / 60 = 0.25 hours. Traveling 15 minutes at 16 miles per hour, Stephen travels 16 * 0.25 = 4 miles. Traveling 15 minutes at 12 miles per hour, Stephen travels 12 * 0.25 = 3 miles. Traveling 15 minutes at 20 miles per hour, Stephen travels 20 * 0.25 = 5 miles. All together, Stephen travels 4 + 3 + 5 = 12 miles. Final answer: 12.