Irish maths test

Irish maths test  Paddy  wants a job, but the foreman won't hire him until he  passes a little maths test. Here is your first  question, the foreman said. "Without using numbers,  represent the number 9." "Without numbers?" Paddy  says? "Dat's easy." And proceeds to draw three  trees.         "What's  this?" the boss asks. "Have you no brain? Tree and  tree plus tree makes 9" says Paddy.   "Fair  enough," says the boss. "Here's your second question.  Use the same rules, but this time the number is  99." Paddy stares into space for a while, then  picks up the picture that he has just drawn and makes  a smudge on each tree.. "Ere ye  go."     The  boss scratches his head and says, "How on earth do you  get that to represent 99?" "Each of them trees is  dirty now. So, it's dirty tree, and dirty tree, plus  dirty tree.. Dat makes 99."   The  boss is getting worried that he's going to actually  have to hire Paddy, so he says, "All right, last  question. Same rules again, but represent the number  100." Paddy stares into space some more, then he  picks up the picture again and makes a little mark at the base of each tree and says, "Ere ye go. One  hundred."     The  boss looks at the attempt. "You must be nuts if you  think that represents a hundred!" Paddy leans  forward and points to the marks at the base of each  tree and whispers, "A little dog came along and pooped  by each tree. So now you got dirty tree and a turd,  dirty tree and a turd, and dirty tree and a turd,  which makes ONE HUNDRED!"   Paddy  is the new supervisor.