How Old Are You?

Nurse: How old are you?

Patient: None of your business.

Nurse: But the doctor must know your age for his records.

Patient: Well, first, multiply twenty by two, then add ten. Got that?

Nurse: Yes. Fifty.

Patient: All right, now subtract fifty, and tell me, what do you get?

Nurse: Zero.

Patient: Right. And that’s exactly the chance of me telling you my age.