Martin Gardner’s Beer Signs On The Highway

Today is the birthday of Martin Gardner, who was an American science and mathematics writer. For many years, beginning in 1957, he wrote a column that appeared in Scientific American. He helped popularize science, and especially math, creating hundreds of puzzles, often collected into books. He passed away in 2010, at age 95. My father-in-law was a huge fan and read most, of not all, of his books.

One of his brain teasers was called “Beer Signs on the Highway,” and originally appeared in Gardner’s column in Math Horizons, in the November 1995 issue. It was also included in the collection My Best Mathematical and Logic Puzzles and also New Mathematical Diversions.

So here it is:

If you think you know the answer or have worked it out, leave your answer in the comments. I’ll post the answer in a couple of days. Good luck.

And the answer is? Drumroll, please:

Could I get a proper drumroll, please?

The Answer:

We can answer this without knowing the car’s speed. If x is the number of signs that the car passes in one minute, then the car will pass 60x signs in an hour. We’re told that the car is traveling at 10x miles per hour, so in 10x miles it will pass 60x signs, and in one mile it will pass 60x/10x signs, or 6. So the signs are 1/6 mile, or 880 feet, apart.