a person takes a trip driving with a constant speed of 89.5 km/h except for a 22 min. rest stop. If the average speed is 77.8 km/h, how much time is spent on the trip and how far does the person travel

\[v _{avg} = \Delta x/\Delta t\] the total time for the trip is the sum of the time for the stop (22 min) + the time for the travel at 89.5 km/h, or \[\Delta t = 22/60 h + t _{89.5}\] Since the average velocity including the stop is 77.8km/h, using teh formula for average velocity \[77.8km/h = \Delta x/\Delta t = \Delta x/[(22/60) h + t _{89.5}]\] rearranging \[77.8 km/h*[(22/60)h + t _{89.5}] = \Delta x\] We know the driver drove at 89.5 km/h for the entire distance (no distance covered while stopped), so \[\Delta x = 89.5 km/h * t _{89.5}\] set the two expressions for the distance equal to each other and solve for the time, then use that value to calculate the distance

Just to check if I did it correctly, does that make 19 minutes spent on the trip and 28.5 km (1dp) traveled?

If you know that much about his speed why didn't you just ask him what time he left and what time he arrived? The math is a lot easier.

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