The train travels at an average speed of 25km/h, to the top of the hill where the midpoint of the trip is. Going down hill, train travels at an average speed of 5km/h. Which of the following is the closest approximation of train's average speed, in kilometers per hour, for the round trip?	Select the correct option
A) 8.5 B) 8.3 C) 2.6 D) 4.2 E) 6.5
Since we're not given a distance to work with, we can TEST any distance that we like. Here, since the speeds are 25 km/hour and 5 km/hour, using a multiple of both 25 and 5 would make the math easiest.   Let's set the Distance up the hill at 50 km.   So, going uphill, we have....   D = (R)(T)   50 = (25)(T)   50/25= 
<gadget id="calculator">50/25</gadget>
<output>2</output>
2= T   2 hours to go uphill   Going downhill, we have....   D = (R)(T)   50 = (5)(T)   50/5= 
<gadget id="calculator">50/5</gadget>
<output>10</output>
10= T   10 hours to go downhill   Total Distance = 100 km   Total Time = 10+2= 
<gadget id="calculator">10+2</gadget>
<output>12</output>
12 hours   Average Speed= 100/12 = 8.3 km/hour   8.3
<result>B</result>
The train travels at an average speed of 25km/h, to the top of the hill where the midpoint of the trip is. Going down hill, train travels at an average speed of 5km/h. Which of the following is the closest approximation of train's average speed, in kilometers per hour, for the round trip?