Find the unit rate for each Olivia and Ryan:
2 2/5 km 15 36 km
------------ * ------- = ------------ = 3.6 km/hr (Olivia)
2/3 hr 15 10 hr
4 1/2 km 2 9 km
------------- * --------- = --------- = 3 km/hr (Ryan)
1 1/2 hr 2 3 hr
Olivia walked 0.6 km/hr faster than did Ryan.