# Check Your Math Before Clicking â€œSendâ€

Submitted by Howard Tayler on September 22, 2009 - 14:18

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

**Second:** Iâ€™ve been getting email from people who are using incorrect formulae for determining the surface area for a cylinder. Iâ€™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, Iâ€™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 weâ€™re leaving the ends out, so itâ€™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. Thatâ€™s not the same as every square kilometer. He wants a thousand square meters, not a million.

Soâ€¦ Divide our result above by 1000, and you have 1,130,972.4 discrete â€œchunksâ€ with a thousand square meters in them. Some chunks might be 10Ã—100 meters, others might be 31.625*31.625â€¦ -ish. The square root of 1000 is in that neighborhood somewhere. Itâ€™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 wasnâ€™t trying to make math funny. This blog-post is more of a stop-gap measure so my mailbox doesnâ€™t fill up with well-meaning-but-erroneous geometric pedantry.

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