SOLUTION: 19. A motorist traveled 115 km on an expressway at an average speed of 92 km/h and another 45 minutes on the other roads. If the average speed for his whole journey was 80 km/h, ho

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: 19. A motorist traveled 115 km on an expressway at an average speed of 92 km/h and another 45 minutes on the other roads. If the average speed for his whole journey was 80 km/h, ho      Log On

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Question 389581: 19. A motorist traveled 115 km on an expressway at an average speed of 92 km/h and another 45 minutes on the other roads. If the average speed for his whole journey was 80 km/h, how far did he travel on the other road
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A motorist traveled 115 km on an expressway at an average speed of 92 km/h and
another 45 minutes on the other roads.
If the average speed for his whole journey was 80 km/h, how far did he travel on the other road
:
Let d = distance traveled on "other road"
:
Change 45 min to .75 hrs
:
Write a time equation: time = dist/speed
115%2F92 + .75 = %28%28d%2B115%29%29%2F80
:
LCM of 92 and 80: multiply by 1840, results:
20(115) + .75(1840) = 23(d + 115)
2300 + 1380 = 23d + 2645
23d = 1035
d = 1035/23
d = 45 km on other road
:
:
Check solution in original equation
115%2F92 + .75 = %28%2845%2B115%29%29%2F80
1.25 + .75 = 2