An old man was running a fairground tent, which proclaimed: 'For fifty dollars I'll teach you to be a mind reader.'
Intrigued by the offer, a teenager entered the tent to try his luck.
'Okay,' said the old guy, handing him a garden hose, 'I want you to hold this hose and look in the end.'
'What for?' asked the teenager.
'It's all part of teaching you to become a mind reader.'
So the teenager, somewhat reluctantly, looked in the end of the hose and saw nothing - just darkness. Then suddenly the old man turned on the tap and water came gushing out all over the young man's face.
'I knew you were going to do something like that!' yelled the drenched teenager.
The old man said: 'Then that'll be fifty dollars.'