SOLUTION: After robbing a bank in Dodge City, a robber gallops off at 12 mi/h. 20 minutes later, the marshall leaves to pursue the robber at 16 mi/h. How long (in hours) does it take the mar

Question 21332: After robbing a bank in Dodge City, a robber gallops off at 12 mi/h. 20 minutes later, the marshall leaves to pursue the robber at 16 mi/h. How long (in hours) does it take the marshall to catch up to the robber?

Found 2 solutions by Paul, JWG:
Answer by Paul(988) (Show Source): You can put this solution on YOUR website!
12(t+20)=16t
12t+240=16t
4t=240

t=60
60minutes=1hour. hence it takes the marshall 1 hour or 60min to catch up to robbers
Answer by JWG(21) (Show Source): You can put this solution on YOUR website!
Another way to look at this problem is by using relative speed. If the robbers are going 12 mph while the marshal is going 16mph, then the marshal has a relative speed of 16-12=4mph.
I convert 20 minutes to 1/3 an hour by putting 20/60=2/6=1/3.
If the robbers is going 12mph, and left 20 minutes before the marshal, then they have traveled (12/1)*(1/3)=4 miles before the marshal left.
Marshal has a relative speed of 4 mph while the robbers have a 4 mile head-start. 4/4=1. Answer: 1 hour.
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