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 16 hours and 81 hours respectively. The ratio of their speeds is?  Choose the correct choice from the following:	A) 4 : 9	B) 9 : 4	C) 4 : 5	D) 4 : 1	E) 4 : 2

Rationale: "let us name the trains a and b . then , ( a ' s speed ) : ( b ' s speed ) = √ b : √ a = √ 81 : √ 16 = 9 : 4 answer : b"
Answer: B