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? Choose the correct choice from the following choices.
A) 22 km/hr
B) 33 km/hr
C) 66 km/hr
D) 44 km/hr
E) None of these
Explanation:   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= 
<gadget id="calculator">18.33/1</gadget>
<output>18.33</output>
18.33m/s   v= 66 km/hr   ANSWER 66 km/hr
<result>C</result>
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?