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# Can you make a few bucks always betting on the 12 at craps?

17 June 2013

Question: My grandfather, who's 92 and lives alone, goes to the casinos by bus every weekday. He loves craps and has a "system." He buys \$31 in dollar chips and bets them one at a time on the 12. As soon as he wins, he quits. He says it's nearly impossible not to hit the 12 in 31 rolls and that he "almost always" wins a few bucks. Is he onto something, or has he just been lucky?

Answer: The chance of a 12 on any roll is 1 out of 36 or 2.78 percent. This is because the dice can land 36 different ways – only one of which, the 6-6, totals 12.

The chance this bet will lose 31 times in a row is 41.76 percent. Five days a week, 50 weeks a year, means 250 games. Your grandfather can expect to lose \$31 in 41.76 percent of those 250. This is 104 games – roughly twice a week overall. The other three times a week, he should break even or win from \$1 to \$30.

If he hits the mathematical average, his 146 wins won't cover his 104 losses. Bad days cost him \$31 but good days earn him less.

Over a year, your grandfather's "system" should work out to set him back around \$3 per session. Depending on where he lives, he's spending \$15 or \$20 for his bus ticket – and the casino refunds from \$5 or \$10 in coin (and sometimes more) and a coupon for a buffet lunch. So he's enjoying time with his cronies, being treated respectfully by the casino staff, eating like a king, getting in on the action, and feeling good about himself for under \$10 or \$15 a day. Assuming he can afford it, where else can the guy get a deal like that?