A man goes from A to B at a speed of 14 kmph and comes back to A at a speed of 10 kmph. Find his average speed for the entire journey?
Answers.
A) 11.6 kmph  B) 12.9 kmph  C) 12.8 kmph  D) 11.9 kmph  E) 12.6 kmph

Rationale: "distance from a and b be ' d ' average speed = total distance / total time average speed = ( 2 d ) / [ ( d / 14 ) + ( d / 10 ] = ( 2 d ) / [ 12 d / 70 ) = > 11.6 kmph . answer : a"
Answer: A