A cyclist rides a bicycle 9 km at an average speed of 12 km/hr and again travels 12 km at an average speed of 9 km/hr. What is the average speed for the entire trip? Pick one:
A) 9.5 B) 9.8 C) 10.1 D) 10.6 E) 11.2
distance = 21 km   time = 9/12 + 12/9 = (81 + 144) / 108 = 225 / 108 = 25/12 hours   average speed = (21 * 12) / 25 = 10.1 km/h   The answer is 10.1.
<result>C</result>
A cyclist rides a bicycle 9 km at an average speed of 12 km/hr and again travels 12 km at an average speed of 9 km/hr. What is the average speed for the entire trip?