Mary and Ann are going sledding. Mary slides down a hill that's 630 feet long at a speed of 90 feet/minute. Ann slides down a hill that's 800 feet long at a rate of 40 feet/minute. How much longer does Ann's trip take than Mary?
Thoughts? Step-by-step reasoning:
First find the total time Mary's trip takes: 630 feet / 90 feet / minute = 7 minutes. Then find the total time Ann's trip takes: 800 feet / 40 feet / minute = 20 minutes. Then subtract Mary's time from Ann's time to find the difference: 20 minutes - 7 minutes = 13 minutes.
Thus, the answer is 13.