Respuesta :
v = speed of car = 90 km/h
u = speed of truck = 50 km/h
d = initial separation distance = 100 m = 0.1 km
They meet at time t such that
vt = d + ut
t(v - u) = d
t = d/(v - u) = (0.1 km) / [(90 - 50) km/h] = 0.0025 hours
95t - .210 = 50t
95t - 50t = 0.210
45t = 0.210
t = 0.210/45
t = 0.0047 km/hr