Question 499532
72 km ------------ 3/2 hour

First part -----36 km----------- 54 km/hr
time = 36/54 = 2/3 hours

Balance time to reach on time = 3/2-2/3= 5/6 hours

Balance distance = 72-36 = 36 km

Speed = distance/time
speed = 36/(5/6)
speed = 36* 6/5
speed = 43.2 km/h second part