SOLUTION: Angelina drove at an average rate of 80 kph and then stopped 20 minutes for gas. After the stop, she drove at an average rate of 100kph. Altogether she drove 250km in a total trip

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Question 278605: Angelina drove at an average rate of 80 kph and then stopped 20 minutes for gas. After the stop, she drove at an average rate of 100kph. Altogether she drove 250km in a total trip of 3 hours including the stop. Which equation could be used to solve for the time T in hours that she drove before her stop?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Angelina drove at an average rate of 80 kph and then stopped 20 minutes for gas.
After the stop, she drove at an average rate of 100kph.
Altogether she drove 250km in a total trip of 3 hours including the stop.
Which equation could be used to solve for the time T in hours that she drove before her stop?
:
Change 20 min to 20/60 = 1/3 hr
:
Let T = time driving at 80 km/hr
then
(3-T-1%2F3) = driving time at 100 km/hr
:
write a distance equation; Dist = speed * time
:
80T + 100(3-T-1%2F3) = 250
80T + 100(2.67-T) = 250
:
80T + 267 - 100t = 250
80T - 100T = 250 - 267
-20T = -17
T = %28-17%29%2F%28-20%29
T = +.85 hrs at 80 km/hr