A group of hikers is planning a trip that will take them up a mountain using one route and back down using another route. They plan to travel down the mountain at a rate of one and a half times the rate they will use on the way up, but the time each route will take is the same. If they will go up the mountain at a rate of 3 miles per day and it will take them two days, how many miles long is the route down the mountain?  Answers
A) 7	B) 8	C) 9	D) 10	E) 11

Rationale: "on the way down , the rate is 1.5 * 3 = 4.5 miles per day . the distance of the route down the mountain is 2 * 4.5 = 9 miles . the answer is c ."
Answer: C