As I was chatting with my cousin Bertha, age 92, this morning we tried to do some arithmetic mentally. I mentioned that a champion runner could run a mile in four minutes.
The "four minute mile" had been a goal of runners for a long time, and was achieved finally. What we tried to do, in our heads, was figure out how many miles per hour this runner achieved.
It got to be funny, we two geniuses trying to reason it out. First Bertha said, "A mile in four minutes is a quarter of a mile an hour." That almost sounded reasonable, for a moment.
"No," I countered. "That is a quarter of a mile per minute. What is a quarter of a mile per minute in miles per hour?"
"There are sixty minutes in an hour," said Bertha, "multiply four times sixty. Two hundred forty."
"Nobody can run two hundred and forty miles per hour," I wailed.
We both laughed.
Later at breakfast, I worked out how many miles per hour a four minute mile runner is traveling-- in my head.
Now, I will leave it up to you to work out, in your head, OR on paper, OR with a calculator. Your choice.