Brain Teaser

During a recent Hope on the Slopes 24-hour ACS skiing fundraiser, I used my watch to track vertical feet throughout the day. The watch isn't perfectly calibrated, but it's reasonably accurate. The watch counts a run any time you make a vertical change of at least 100 feet (so when you ride up the lift you are going up at least 100 feet, it counts that as a run.) We started skiing at 9:30am and didn’t look at the watch until 7:30pm. I only skied on one lift and it had a vertical rise of 1210 feet. At that time I was surprised to see that I had skied 20,100 feet and 41 runs.

Clearly 41 runs * 1210 feet = 49610 feet. The watch incorrectly said that I had skied 20,100 but had the correct number of runs. Huh?

I had plenty of time to think this over while I was riding the lifts later that evening. Eventually I realized that the watch was actually tracking all of my vertical feet correctly. Do you know what happened?

I'll make another post in a couple days with the answer. Leave a comment if you know the answer.

These additional facts may or may not help you:

  • I wore the watch the whole time.
  • The watch was on the whole time (remember that it correctly counted all 41 runs.)
  • There was no major weather event that changed the barometric pressure.
  • It was accurately tracking my vertical feet the entire time.
  • I didn't stop or restart the watch at any point (again, remember that it showed 41 runs.)
  • The highest number I have ever seen it record previously is 28,000.
  • 1210 is the vertical rise of the lift. One trip down the ski run would show slightly more than that due to little hills in the middle of the run. None of those hills are higher than 100 feet so they don't make the watch think they are extra runs.