Question

A man on a road trip drives a car at different constant speeds over several legs of the trip. He drives for 15.0 min at 50.0 km/h, 19.0 min at 85.0 km/h, and 55.0 min at 60.0 km/h and spends 25.0 min eating lunch and buying gas.
a. What is the total distance traveled over the entire trip (in km)?
b. What is the average speed for the entire trip (in km/h)?

Answer 1

Answer

given

Case 1-Speed of car 50 Km/h for 15 min

Case 2-Speed of car 85 Km/h for 19 min

Case 3 - Speed of car 60 km/h for 55 min

lunch break time = 25 min

a) total distance travel

   we know,

    distance = speed x time

 $D = 50 \times \dfrac{15}{60} + 85 \times \dfrac{19}{60} + 60\times \dfrac{55}{60}$

  D = 94.42 Km

b) $average\ speed = \dfrac{total\ distance}{total\ time}$

   $average\ speed = \dfrac{94.42}{\dfrac{15}{60}+\dfrac{19}{60}+\dfrac{55}{60}+\dfrac{25}{60}}$

$average\ speed = 49.69\ km/h$