Creative Question:

There are 250 million people in the U.S. Let's suppose that the number of skis is 15 percent of that, or 37,500,000. Of those, let's figure that 21,175,000 of them own skis, leaving the number who rent at 9,325,000. Then let's add the number of tourists who ski, say, one million. So the grand total of renters would be 10,325,000.
Now let's assume that the renters who live here take three trips a year, so three times 9,325,000 is 27,975,000 and add that with 1,000,000 is 28,975,000.