Problem:
On a trip to the beach, Anh traveled miles on the highway and miles on a coastal access road. He drove three times as fast on the highway as on the coastal road. If Anh spent minutes driving on the coastal road, how many minutes did his entire trip take?
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Solution:
Anh's speed on the coastal road was 20 miles per hour because he drove 10 miles in half an hour. This implies that Anh traveled 60 miles per hour on the highway, and so it took Anh 50 minutes to drive the 50 miles. Anh's entire trip took 30 + 50 = 80 minutes.
Because Anh drives three time as fast on the highway, he needs only = 10 minutes to drive 10 miles on the highway and five times 10 minutes to drive 50 miles on the highway. Thus his total time is 30 +5 (10) = 80 minutes.
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions