Answer: 0.42 km/min
Step-by-step explanation:
total distance traveled(in meters) = 210m
total distance traveled(in km) = 210 ÷ 1000 = 0.21 km
total time taken(in seconds) = 30 s
total time taken(in minutes) = 30 ÷ 60 = 0.5 s
speed =(distance traveled)÷(time taken)[in km/min] = 0.21 ÷ 0.5 = 0.42km/min