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To Grandma's House We Shall Need to Go....

The distance to grandma's house is 100 miles. The freeway speed limit is 55 mph half the distance, and 65 mph the rest of the distance. Cars A and B start along the same route together. Car A uses a rest stop for 15 minutes in the 55 mph stretch, while Car B stops for 15 minutes during the 65 mph stretch. We assume that at all other times, both cars go the maximum legal speed limit. Which car gets to grandma's house first?


Hint: Can you use d = rt? Does it matter when you stop at a rest station?


Solution Commentary: This problem has created lots of arguments amongst students and teachers. Send me your suggested solutions (andf reasoning) and perhaps we can start some more arguments!