a model airplane flies 18 feet in 2 seconds. What is the airplane's speed in miles per hour?

Answer 1

It travels 9 feet per second.

9 * 60 * 60 = 32,400 feet per hour

To find the miles per hour, divide:

32,400 / 5,280 = ? miles per hour

Answer 2

long ago I memorized a conversion factor:

60mph=88fps

18/88=x/60 will do it.

Answer 3

oops...

9/88=x/60 will do it.

Answer 4

When I was a kid, my dad was appalled that I didn't know that 5,280 feet = 1 mile. Since we were on a long car trip, I had plenty of time to memorize that number. I still remember it after 60 years. <g>