"At the races" joke

The Young Whipper-Snapper (TYWS) took MrsYWS to the races one fine Sunday. There they met Maury, an old Army buddy of TYWS.
"Hey! Maury! How's it goin?" says TYWS.
"Cool enough," says Maury, "I've come to bet.
"Great," says TYWS, "you can explain it to me, because I don't know anything about the track."
"Me neither," confesses Maury, "I just play random combinations, and that works like a charm every time. Here ya go, lemme help you pick some numbers. How long you and the missus been married?"
"15 years."
"And how many times a week do yo make love?"
"7."
"And how many kids you got?"
"2."
"And, finally, what's the last number in your house number?"
"9."
"Great!" says Maury. "I'm gonna fix you up with 15-7-2-9."
The race takes place, but the winning combinatin is 15-1-2-9.
That's when MrsYWS knocks TYWS over the head with her purse: "Fool! If you had told him the truth, we'd be RICH!"