Arthur and Betty start walking toward each other when they are 100 m apart. Arthur has a

speed of 3.0 m/s and Betty has a speed of 2.0 m/s. Their dog, Spot, starts by Arthur's side at

the same time and runs back and forth between them at 5.0 m/s. By the time Arthur and

Betty meet, what distance has Spot run?

Hello there.

Arthur and Betty start walking toward each other when they are 100 m apart. Arthur has a

speed of 3.0 m/s and Betty has a speed of 2.0 m/s. Their dog, Spot, starts by Arthur's side at

the same time and runs back and forth between them at 5.0 m/s. By the time Arthur and

Betty meet, what distance has Spot run?

100 m

The distance covered by Arthur is

3t

The distance covered by Betty from where Arthur started is

100 - 2t

They meet each other when this distance is equal

3t = 100 - 2t

t = 20 s

Since the dog has a constant speed of 5m/s, the distance that Spot has run is

5 m/s (20s) = 100 m