unit10 The Art of Smart Guessing 巧妙猜测的艺术（在线收听）

The Art of Smart Guessing

Several years ago, interviewing candidates for a job, I grew tired of asking "What experience do you have?" So I decided on a one-question quiz to find out how resourceful a thinker the new hire might be. Here it is:

You are on a yacht sailing the Pacific Ocean. Your navigator announces you are over the deepest point, the Mariana Trench. Just then, a clumsy guest accidentally drops a 12-pound cannonball, over the side. How long will it take for the cannonball to reach the bottom of the ocean!

Before reading on, please try to solve this yourself--paying special attention to how you might solve it.

Did you make a completely wild guess because "there wasn't enough information"? Did you get too bogged down in the details trying to come up with the "exactly right" answer? Or did you zero in on the two most important problems--how deep is the Mariana Trench and how fast might a cannonball fall through the water-- then hazard a guesstimate?

Most of my candidates simply made a wild guess, thinking that if they couldn't be 100-percent right, there was no use trying to be 95-percent right. Rarely was someone willing to risk an approximation.

What does this have to do with business or creativity? A great deal. In the real world, we frequently need to make decisions when the full information does not exist. From what foods we eat to how to raise our kids, creative people must think for themselves. There may not be the time or the money to make sure of all your decisions. Your best guess will often be the best you can do.

Suppose, for example, you've been asked to write a marketing plan for a new telephone device that will send your name, company, address and telephone number to a visual display or printer on another person's phone. In addition to conventional outlets like mass merchandisers and electronics stores, you'd like to know the number of "phone stores" in the United States. Unfortunately, this figure is not available, either from market-research houses or from the U.S. government. What do you do?

One solution would be to go to your local library, pull out a few phone directories from around the country, turn to the Yellow Pages and start counting. You could then guesstimate how many stores there were nationwide, based on the number of stores per 100,000 people in each of the cities you counted. This, by the way, is exactly what a marketing consultant I know did for a large telecommunications client.

The question about phone stores was an example of what scientists call a Fermi problem, named after Nobel Prize-winning physicist Enrico Fermi , who used problems such as this to teach his students how to think for themselves. A Fermi problem does not contain all the information you need to solve it precisely.

Fermi is said to have once asked his university students how many piano tuners there were in Chicago. To answer the question, he recommended breaking it down into smaller, more manageable questions , and then having the courage to make some guesses and assumptions. How many people live in Chicago? Three million would be a reasonable estimate. How many people per family? Assume an average of four. How many families own pianos? Say one out of three. Then there are about 250,000 pianos in Chicago. How often would each be tuned? Maybe once every five years. That makes 50,000 tunings a year. How many pianos can one tuner tune in a day? Four? And how many in a year? Assuming 250 working days, one tuner can handle 1,000 pianos a year.

So there's work for approximately 50 piano tuners in Chicago-- which; as it turns out, is reasonably close to the actual number in the Yellow Pages.

Why was guesswork so accurate? The law of averages is partly responsible. At any point, your assumptions may be too high or too low. But because of the law of averages, your mistakes, will frequently balance out.

Here's another puzzle. You probably already know that black absorbs the most heat, while white reflects the most. But what about other colors in between? How could you find the answer? Hint: it's wintertime, but not too cold.

Ben Franklin's solution was elegant. He simply laid broadcloth samples of various colors on the snow on a sunny morning. "In a few hours," he reported, "the black, being warmed most by the sun, was sunk so low as to be below the stroke of the sun's rays; the dark blue, almost as low; the lighter blue not quite so much as the dark; the other colors, less as they were lighter, and the quite white remained on the surface of the snow, not having entered it at all."

One of my favorite "guesstimators" is Weston, Conn., inventor Stan Mason, who developed microwave cookware specially designed to position food in the best spot for cooking.

To do this, Mason needed to know where the microwave's "hot spots were -- the place where the rays hit the food with the highest intensity. To find out, he put shelves of unpopped popcorn kernels in the microwave and watched to see which kernels popped first. He discovered a pattern in the oven's hottest rays: they weren't in the corners or at the center, but in the shape of a mushroom cloud.

Then he designed cooking dishes to fit the pattern. He had come up with a resourceful way to approximate the answer rather than using scientifically sophisticated testing equipment.

Fermis would have approved.

By the way, the Mariana Trench is about six nautical miles deep, and a cannonball drops at a rate of ten feet per second. So it took the cannonball about an hour to reach the bottom of the trench.

Could this be guessed? If you know that Earth's highest point Mount Everest, is 29,000 feet, you might reasonably conclude that its lowest point would be close to the same distance. Then you might imagine that a heavy object would take one second to fall through the water of a 10-foot-deep swimming pool. These estimates would bring you close enough to the correct answer.