SOLUTION: A bicyclist rode from point A to Point B at an average speed of 30 km/hr. Without stopping, he returned from Point B to Point A, following the same route, at an average speed of 20

Algebra ->  Real-numbers -> SOLUTION: A bicyclist rode from point A to Point B at an average speed of 30 km/hr. Without stopping, he returned from Point B to Point A, following the same route, at an average speed of 20      Log On


   

Question 634512: A bicyclist rode from point A to Point B at an average speed of 30 km/hr. Without stopping, he returned from Point B to Point A, following the same route, at an average speed of 20 km/hr. What was the average speed in km/hr over the course of the ride?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A bicyclist rode from point A to Point B at an average speed of 30 km/hr.
Without stopping, he returned from Point B to Point A, following the same
route, at an average speed of 20 km/hr.
What was the average speed in km/hr over the course of the ride?
:
Let a = the average speed for the round trip
Let d = one-way distance
:
Write a time equation, time = dist/speed
:
A-B time + B-A time = Total time
d%2F30 + d%2F20 = %282d%29%2Fa
We don't need d, divide thru by d
1%2F30 + 1%2F20 = %282%29%2Fa
multiply by 60a, resulting in
2a + 3a = 2(60)
5a = 120
a = 120/5
a = 24 km/h is the average speed for the round trip