66. A and B go cycling in the same direction with speeds of 6 km/hr and 12 km/hr. A car from behind passes them in 9 and 10 seconds respectively. What is the speed of the car?

✅ The correct answer is option C. 66 km/hr.
The relative speed of A and B is 6 km/hr = 1.67 m/s

As the car passes A after 10s, the distance between A and B after 10s (i.e. at 11th second) is the distance covered by car in 1 second.

Therefore, at t = 11, d = 1.67 * 11

d = 18.33 m

v = d/t = 18.33/1 = 18.33m/s

v = 66 km/hr