Witty Murphy

A construction site boss was interviewing men for a job, when along came Murphy. The boss though "I'm not hiring that lazy Irishman", so he decided to set a test for Murphy, hoping he wouldn't be able to answer the questions, and he'd be able to refuse him the job without getting into an argument.
The first question was:
- Without using numbers, represent the number 9.
So Murphy says:
-Dat's easy - and proceeds to draw three trees.


The boss says:
- What the hell is that?
Murphy says:
- Tree and tree and tree makes nine.
- Fair enough - says the boss. - Second question, same rules, but represent the number 99.
Murphy stares into space for a while, then makes a smudge on each tree.
- Der ya go sir - he says.
The boss scratches his head and says:
- How on earth do you get that to represent 99?
Murphy says:
- Each tree is dirty now! So it's dirty tree and dirty tree and dirty tree, dats 99.
The boss is getting worried he is going to have to hire him, so he says:
- All right, question three. Same rules again, but represent the number 100.
Murphy stares into space again, then he shouts
- Got it!
He makes a little mark at the base on each tree, and says:
- Der ya go sir 100.
The boss looks at Murphy's attempt and thinks "Ha! Got him this time!"
- Go on Murphy, you must be mad if you think that represents a hundred.
Murphy leans forward and points to the mark at the tree bases, and says:
- A little dog comes along and craps by each tree, so now you've got dirty tree and a turd, dirty tree and a turd and dirty tree and a turd, which makes one hundred. When do I start me job?