Tom drives from town R to town B, driving at a constant speed of 60 miles per hour. From town B Tom immediately continues to town C. The distance between R and B is twice the distance between B and C. If the average speed of the whole journey was 36 mph, then what is Tom's speed driving from B to C in miles per hour? Choose the correct choice from the following choices.
A) 12 B) 20 C) 24 D) 30 E) 36
Let's assume that it takes 4 hours to go from point R to B. Then the distance between them becomes 240 which makes distance between B and C 120. (240+120)/(4+x) gives us the average speed which is 36. You find x=6. So the question simplifies itself to   120/6= 
<gadget id="calculator">  120/6</gadget>
<output>20</output>
20   Hence the answer is 20.
<result>B</result>
Tom drives from town R to town B, driving at a constant speed of 60 miles per hour. From town B Tom immediately continues to town C. The distance between R and B is twice the distance between B and C. If the average speed of the whole journey was 36 mph, then what is Tom's speed driving from B to C in miles per hour?