Question

Franklin rides his bike to the beach averaging 18mph. He rides home along the same route. What speed must he average on the way home if he wants to average 21 miles per hour for the round trip?

Answer 1

Explanation:

We will have to apply the harmonic mean which is (2ab)/(a+b). This is because they want to go the SAME DISTANCE but faster, meaning less time. A very common mistake is just (18+x)/2=21 which is only if they travel the SAME TIME. After you plug the numbers in, you should get (36x)/(18+x)=21. Solving this will give you 25.2 mph back.

Answer 2

• Answer:

24 mph

• Explanation:

Hi there !

Vm = 21mph

V1 = 18mph

V2 = ?

Vm = (V₁ + V₂)/2

2Vm = V₁ + V₂

V₂ = 2Vm - V₁

replace Vm ; V₁

V₂ = 2×21mph - 18mph

= 42mph - 18mph

= 24 mph

Good luck !