"I was behind you in McDonald's"

A man decided to have a face lift for his birthday. He spends $5, 000 and
feels really good about the result. On his way home he stops at a newsstand and
buys a paper.
Before leaving he says to the sales clerk, "I hope you don't mind me asking,
but how old do you think I am?"
"About 35, " was the reply.
"I'm actually 47, " the man says happily.
A little while later he goes to McDonald's for lunch and asks the order taker
the same question, to which the reply is, "I'd guess that you're 29?"
"Nope, I am actually 47." He's starting to feel really good about himself.
While standing at the bus stop he asks an old woman the same question.
She replies, "I am 85 years old and my eyesight is going. But when I was young
there was a sure way of telling a man's age. If I put my hand down your pants
and play with your penis for ten minutes I will be able to tell your exact
age."
As there was no one else around the man thought what the hell and let her
slip her hand down his pants.
Ten minutes later the old lady says, "OK, it's done. You are 47, "
Stunned the man says, "That was brilliant! How did you do that?"
The old lady replies, "I was behind you in McDonald's".