Final answer:
The average speed of the car is 77.8 km/h.
Step-by-step explanation:
The average speed of a car can be calculated by dividing the distance traveled by the time taken. In this case, the car travels 21 km in 16 minutes. To find the average speed in km/h, we need to convert the time from minutes to hours. There are 60 minutes in an hour, so 16 minutes is equal to 16/60 = 0.27 hours. Now, we can calculate the average speed:
Average Speed = Distance / Time
Average Speed = 21 km / 0.27 hours = 77.78 km/h
Therefore, the average speed of the car is 77.8 km/h (rounded to 1 decimal place).