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 answer:
A) 12
B) 20
C) 24
D) 30
E) 36

Rationale: 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 = 20 hence the answer is b .
Answer: B