Answer:
40 km/h
Step-by-step explanation:
s = ut where s - Distance
u - Speed
t - Time
when t = 10 min
= 10/60 hours
S1 = 30 * 10/60
= 5km
when t= 20 min
= 20/60 hours
S2 = 45 *20/60
= 15 km
Then total distance = S1 + S2
= 5 + 15
= 20 km
Total time period = (10 + 20 ) / 60 hours
= 1/2 hours
Then average speed = U
S = UT
U = S/ T
= 20/ 0.5 km/ h
= 40 km/ h
