Answer:
30 km/hr
Explanation:
There are no stops so the equation is just d = r*t
r = 15 km
t = 30 minutes = 30/60 hour = 1/2 hour = 0.5 hours.
r = d/t
r = 15 km / 0.5 hour
r = 30 km / hour
That is a pretty good clip for someone who is just a 3 times a week cyclist.
