How much rain does it take to produce an inch of snow?
— F.S., Chicago, Ill.
In the U.S., on average, an inch of rain produces about 13 inches of snow. But the rain-to-snow ratio in any particular snowstorm varies widely, depending on local weather conditions, which include many factors. For example, an inch of rain may result in only six inches of heavy, wet snow — the kind that you hate to shovel but the kids love to build into towering snowmen. Or it may dump three feet of the dry, powdery stuff that you can't pack into a good snowball but delights skiers and snowboarders and students when school is canceled!
I have always associated multiplication with addition (more), and division with subtraction (less), so I don't understand current phrases such as "three times less" and "twice as small." Can you explain?
— Jack Clark, Apex, N.C.
Yes. Those phrases, which make many of us wince when we hear newscasters and commentators use them, are just plain mathematically illiterate! In arithmetic, the term "times" means "instances of," in the way "two times three" means "two instances of three," or six. A person who says "three times less" probably means "one-third as much," and one who says "twice as small" likely means "half as small." In short, they have it backward!
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