a mathematician and an engineer are sitting next to each other on a long flight. the mathematician leans over to the engineer and asks him if he wants to play a fun game. the engineer just wants to sleep so politely refuses and turns away.

 

the mathematician persists and explains that the game is really simple and lots of fun. he says " i ask you a question and if you don't know the answer, you give me a fiver. then you ask me a question and if i don't know the answer i give you a fiver."

 

again the engineer politely declines and tries to get some sleep. the mathematician is getting agitated by now and goes on to say "OK, if you don't know the answer you give me a fiver and if i dont know the answer i give you a fifty...!"

 

this gets the engineers attention and added to that the resignation that the mathematician won't be satisfied until he plays along agrees to the game. the mathematician asks the first question. "what is the distance from the earth to the moon?"

 

the engineer says nothing but takes out his wallet and hands the mathematician a fiver. then the engineer asks the mathematician "what goes up a hill on three legs but comes down on four?"

 

the mathematician hasn't a clue, he searches all references on his laptop for any information, uses the modem and in flight phone to scour the internet, finally he emails all his colleagues for the answer but to no avail.

 

after a couple of hours searching the mathematician wakes up the engineer and hands him a fifty. the engineers takes it and goes back to sleep.

 

after another hour the mathematician wakes the engineer again and asks him "what does go up a hill on three legs and comes down on four?" the engineer calmy pulls out his wallet, hands the mathematician another fiver and goes to sleep.