Two trains, one from Howrah to Patna and the other from Patna to Howrah, start simultaneously. After they meet, the trains reach their destinations after 9 hours and 36 hours respectively. The ratio of their speeds is?  Choose one.
A) 6 : 5 B) 6 : 3 C) 4 : 4 D) 4 : 8 E) 4 : 1

Rationale: "let us name the trains a and b . then , ( a ' s speed ) : ( b ' s speed ) = √ b : √ a = √ 36 : √ 9 = 6 : 3 answer : b"
Answer: B