SOLUTION: To get to his cousin�s house, Mark must drive 135 km on the expressway and then 45 km along the country road. If the entire trip takes 5 hours and he can travel 3 times faster on

Question 989007: To get to his cousin�s house, Mark must drive 135 km on the expressway and then 45 km along the country road. If the entire trip takes 5 hours and he can travel 3 times faster on the expressway than on the country road, how fast does he travel on the expressway?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Mark must drive 135 km on the expressway and then 45 km along the country road.
If the entire trip takes 5 hours and he can travel 3 times faster on the expressway than on the country road, how fast does he travel on the expressway?
:
Let s = his speed on the country road
It says,"he can travel 3 times faster on the expressway than on the country road," therefore:
3s = speed on the expressway
:
Write a time equation, time = dist/speed
:
Time on Ex + Country Rd time = 5 hrs
+ = 5
multiply equation on by 3s to clear the denominators
3s* + 3s* = 5(3s)
cancel denominators and you have
135 + 3(45) = 15s
135 + 135 = 15s
270 = 15s
s = 270/15
s = 18 mph on country road
:
"how fast does he travel on the expressway? "
3*18 = 54 mph on the expressway
:
:
Confirm this, find the actual time at each speed
135/54 = 2.5 hrs
45/18 = 2.5
---------------
total time: 5 hrs

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