George Shaffner believes in living life by the numbers. Literally, he does.

The year one of his sons considered leaving high school before graduating, Shaffner grabbed his calculator, punched in some Bureau of Labor stats, and computed how much more income college and high school grads earned over a lifetime compared to high school dropouts. With the prospect of earning about a half-million dollars more, his son stayed in school.

When a star colleague's workplace conceit began affecting the morale of the other workers, Shaffner calculated the negative impact the prima donna was having on office productivity. The bottom line? A convincing case for firing the most productive individual.

When Shaffner's other son was "accumulating speeding tickets the way some sports fans collect baseball cards," he figured the odds of getting caught -- illustrating a fundamental mathematical law: With repetition, those odds move rapidly toward certainty.

"I guess I was picking some low-hanging fruit in the early going, but it was pertinent fruit," Shaffner says.

He isn't apologizing for what became the underlying lesson of his new book, "The Arithmetic of Life" (Ballantine Books, $16.95) -- that math needs to be pertinent and practical. He contends that an intelligent application of the most basic mathematical tools -- addition, subtraction, multiplication and division -- can help solve almost any problem in the puzzling equation called life.

In fact, while he does a number on plenty of "nickel-and-dime" problems, Shaffner got started on the book when confronted by one of life's biggest mysteries: What happens once your number's up?

"My mother-in-law started it" three years ago, says Shaffner, 51, who lives near Seattle. He took a break from more than 20 years of solving problems in the high-technology field to write the book. "She was feeling very down because her brother-in-law was losing his battle with cancer."

In her eighties and a devout Catholic, she usually sported a cheery outlook. But she seemed to be struggling with her own mortality and doubts about afterlife, says Shaffner. Figuring a hug wouldn't do the trick, he decided to help her by applying mathematical principles, a little common sense, some chaos theory and inferential logic to make a secular case for life after death.

Shaffner says "the mathematical perspective" provides abundant clues supporting the probability of life after death: It's overwhelmingly unlikely, he reasons, that humanity is the singular exception to what science might call the "Rule of Always More," which states there are always more dimensions of scale and complexity to our own existence than we can ever know in this lifetime. "You don't get any binary conclusion that you are going to Heaven or going to Hell," he says. "But there may be an infinity of other outcomes."

"You don't get any binary conclusion that you are going to Heaven or going to Hell." -- George Shaffner

His calculations uplifted his mother-in-law, and they set the benchmark for some of the book's other chapters that explored hard questions, like the odds on intelligent life elsewhere in the universe, and the likelihood of Earth surviving overpopulation.

Though not all the chapters paint quite the apocalyptic picture as the book's publicity: "He makes clear if we don't have a handle on basic math . . . we could all go down for the count," some of the findings did catch the die-hard numeralist off guard.

"I didn't expect it would turn out the one thing mankind can do to reduce statistically the odds of death by misadventure is act like a woman," he says of the evidence that women make up about 50 percent of the population but account for 29 percent of deaths from accidents, homicides and suicides.

Shaffner doesn't claim crunching numbers solves everything. Take his analysis of the cost of smoking -- spurred by his 16-year-old taking up cigarettes. Smoking seems a cheap enough vice, especially when he figures the cost to be about three cents per minute.

But that's a smokescreen, says Shaffner, who calculated the cost of a 16-year-old smoker graduating to a pack and a half a day and maintaining it until age 66. If the price of a pack never increases, he will spend more than $80,000 on cigarettes. Adjusted for inflation? "He'll spend more than $300,000 in a lifetime to die five or six years sooner," says ex-smoker Shaffner, who adds that even those figures haven't persuaded his wife and children to stop smoking.

"There are so many of these things out there where numbers are really important. It's not a very good time to be . . . a math refugee," says Shaffner, who says moving most students toward theoretical mathematics and away from useful mathematics is a mistake our educational system makes.

"We train every little John and Mary as if they are all going to be astrophysicists or exobiologists," says the college math major whose own love for numbers began as a boy scouring the stats on the back of his baseball cards. "We are shaped and pushed into algebra II and calculus -- and who cares? I've been in business for 29 years and I have never used calculus for one moment.

"I keep waiting for some guy with a PhD and a bunch of extra initials behind his name to show up and say I haven't proven anything. But the things of day-to-day life don't need proof, they need some good examples and statistics."

Tailgating, for example. "Tailgating is the 20th-century archetype of the dimwit decision," says Shaffner, explaining that tailgaters cause one-sixth of all traffic accidents while the payoff is getting to their destination about two seconds sooner.

"The downside in tailgating is 21,000 times the upside," he says, adding that tailgaters also need to factor the odds of dying into their bumper hugging. "I would much rather that the person behind me in the 7,000-pound sports utility vehicle understand a little bit about basic statistics. And that's what I think we need to teach."

But the mathematical principle Shaffner would most like his readers to take home requires no calculator. "A single act of reason is more valuable than a thousand acts of ignorance," he concludes. "Intelligence is not just a gift, it's a choice. I sure would like for it to be popular for people to make that choice a lot more often than they do."