On a trip covering 250 km, a bicyclist travels the first 100 km at 20 km per hour and the remainder of the distance at 15 km per hour. What is the average speed, in km per hour, for the entire trip?
Pick one:  A) 15.8  B) 16.3  C) 16.7  D) 17.2  E) 17.5
time 1 = 100 / 20= 
<gadget id="calculator">100 / 20</gadget>
<output>5</output>
5 hours   time 2= 150 / 15= 
<gadget id="calculator">150 / 15</gadget>
<output>10</output>
10 hours   total time= 15 hours   average speed = 250 / 15 = 16.7 km/hr   The answer is 16.7.
<result>C</result>
On a trip covering 250 km, a bicyclist travels the first 100 km at 20 km per hour and the remainder of the distance at 15 km per hour. What is the average speed, in km per hour, for the entire trip?