Feet per secounds

Question

Mary runs at a constant speed of 18feet per second, while her little brother Billy runs at a constant speed of 14 feet per second. How far would Mary have to run to catch up with Billy if she gave him a 60 foot head start?

Answer 1

Let Mary's velocity = V_m = 18 ft/sec

Bill's velocity = V_b = 14 ft/sec

t = Time in seconds

In general, Velocity = DIstance/Time or Distance = Velocity x Time

At time zero, Billy's distance = 60 + 14t

Mary's distance = 18t

When Mary catches Billy, their distances are equal or 60 + 14t = 18t

Solving for t, we find that t = 15 seconds

Mary runs 18(15) ft in that time or Mary's distance = 270 ft