Answer: 76.8km/hr
Step-by-step explanation:
PT1
sp1 - 30km/hr
d1 - 60km
60 divided by 30 = 2hrs
PT2
sp2 - 160km/hr
d2 - 180km
180 divided by 30 = 1hr, 7min, 30sec (1.125)
PT3
Total Time Taken - 2hrs + (1:07:30) 1.125 = 3.125hrs
Avg. Speed - (60km + 180km) divided by 3.125hrs
60km + 180km = 240
240km divided by 3.125 = 76.8km/hr