An old dead and mute man come to the ticket counter of the subway station and asked for tickets.
Each ticket cost 50 cents.
The old man gave him an exact one dollar and the ticket clerk gave him 2 tickets without even confirming.
How did the clerk know that the man needed 2 tickets?
The deaf and mute man gave 4 quarters so the ticket clerk knew that he wanted 2 tickets. Otherwise, he would have only given 2 quarters.
