# Check Your Math Before Clicking Send Tuesday September 22, 2009 • Howard Tayler

First: Yes, the very original-most version of Tuesday's strip had a math error in it. It's gone now. Hat tip to Matija for telling me to move my decimal point. Clear your cache and we can proceed.

Second: I've been getting email from people who are using incorrect formulae for determining the surface area for a cylinder. I've also gotten email from people who used the right formula but misread the results (which is how my original error crept into the strip, but I digress.) Finally, I'm getting email from people who are misunderstanding what Kevyn is asking for.

So: The formula for the surface area of a cylinder is (Circumference * length) + ends. In this case we're leaving the ends out, so it's just C*L.Circumference is 2pi*r, or pi*diameter.

Using the dimensions of Credomar in meters:

(6000*3.14159)*60,000 = 1,130,972,400 square meters.

Kevyn wants one teraport for every thousand square meters. That's not the same as every square kilometer. He wants a thousand square meters, not a million.

So... Divide our result above by 1000, and you have 1,130,972.4 discrete "chunks" with a thousand square meters in them. Some chunks might be 10x100 meters, others might be 31.625*31.625... -ish. The square root of 1000 is in that neighborhood somewhere. It's close enough for engineering work. (The pure mathematicians in the room should have covered their ears for that.)

This would have made a great footnote, but at the time I wrote the strip I wasn't trying to make math funny. This blog-post is more of a stop-gap measure so my mailbox doesn't fill up with well-meaning-but-erroneous geometric pedantry.

It will probably still fill up with hate-mail from the pure-math crew.