You've all heard kids say it before in a lesson.
"When am I ever going to use that in real life?"
And this applies to lots of things where there's a formula or a bit of algebra and some abstract thinking.
Well, yesterday was Sunday and I was looking to find a church somewhere in San Francisco that I wanted to visit. I found it on a map. It is called the City Church on Sutter St - great church by the way if you're looking for somewhere.
Anyway, looking at the map, I had a few choices. I could go straight down Jones Street until I hit Sutter Street and then turn right (the red line).
Or I could take the hypotenuse (the green line) - much shorter!
This wasn't some clever mathematical calculation - it is just common sense. The hypotenuse is going to be shorter.
But how much shorter?
Well, if each of the other sides is about 2.5kms, then....
a2 + b2 = c2
2.52 + 2.52 = c2
c2 = 6.25 + 6.25
c2 = 12.5
c = 3.5
So I saved myself about 1.5km but cutting along the hypotenuse.
Of course, I couldn't exactly go straight along the green line - there were houses and things in the way. My path looked a bit more like this:
Still, pretty sure it saved me some time. I got there 45 minutes before it started - which was good because I hadn't written down the exact address so I needed to walk around a bit to find the actual building.
Well, who would have thought to look in the Russian Centre building?
After posting this story, there was a certain frenzy on Twitter with several astute minds asking about the conclusions I had drawn - thanks
@mathinyourfeet @ddmeyer @nathankraft1 @smithnj @tieandjeans @emilyrolsen @mauidoe @fawnpnguyen @ajm2035 and any others I forgot to mention.
The concerns raised were specifically:
- Was the green route actually any shorter? - because it looks like it has the same vertical and horizontal distances as the red lines
- If I was driving, did I take into account the number of left hand turns I would need to do that might slow me down
- Were there any red lights I had to stop for?
- And how much stopping and starting would you do if you had to make all those turns?
- And what would that do with your mileage?
Well, I was walking and got to cut a few corners but I take the point. Even though the green path is fractionally shorter when you walk it (by cutting the corners etc), it certainly isn't the same as going in a straight line.
And I certainly didn't save 1.5kms by doing it.
Oh, for the wings of a dove....