Bernie left home, riding his bike at a rate of 15 miles per hour

Question

Bernie left home, riding his bike at a rate of 15 miles per hour. Charlie left 1 hour later, biking at a rate of 20 miles per hour. How long will it take Charlie to catch up to Bernie?

Answer 1

Bernie distance = 15*t

Charlie distance = 20*(t-1)

15t = 20t - 20

-5t = -20

t = 4

3 hours

4*15 = 60

3*20 = 60