Q5) A race car circles 10 times around a circle with a diameter of 7 km track in 50 min. Using SI
units, the average speed for the ten cycles is approximately given as:

100*pi/3 m/s
If d=10, r=5. Circumference is 2*pi*r.
10pi would be one track length.
Since he goes around 10 times, we can multiply that by 10.
100pi is his total distance in kilometers. If we multiply that by 100, we get his distance in meters.
10,000*pi m.
If we multiply the 50 mins by 60, we can get the number of seconds it takes.
300 seconds.
10000*pi/300 m/s
Simplified: 100*pi/3 m/s