We can answer this using one of the equations of linear
motion:
v = d / t
where:
v = velocity
d = distance
t = time
In the problem, we are asked to find for the time in
which Driver B will catch up to Driver A. Therefore, find the time when dA = dB. Rearranging the
equation and equation dA and dB will result in:
vA * tA = vB * tB
---> 1
It was given that:
vA = 68 mph
tA = tB + 3 (since person A was travelling 3 hours
earlier)
vB = 85 mph
tB = unknown
Substituting into equation 1:
68 * (tB + 3) = 85 * tB
68 tB + 204 = 85 tB
tB = 12 hrs
Therefore driver B would catch up to driver A after 12
hrs.
