Question

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?

Answer 1

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

Answer 2

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