Answer:
r = 100 km/hr is the average speed of the car.
Explanation:
The formula which relates distance d, time t, and speed or rate of travel r is:
d = rt.
We're given that the distance traveled d = 50 km and the time t traveled = 30 minutes = 1/2 hr. Substituting this given information into the distance-rate-time formula for d and t to find r, we get:
50 km = r(1/2 hr)
Now, dividing both sides by 1/2 hr, we have:
50 km/(1/2 hr) = [r(1/2 hr)]/(1/2 hr)
50 km/(1/2 hr) = r[(1/2 hr)/(1/2 hr)]
[50 km/(1/2)] km/hr = r[(1/2 hr)/(1/2 hr)]
50(2/1) km/hr = r[1]
100 km/hr = r[1]
r = 100 km/hr is the average speed of the car.