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Vampyria
October 5th, 2013, 10:23 AM
I have bangs, and I can't put them in a ponytail with the rest of the hair to measure my circumference. My circumference is 3.25 without bangs and bangs have around 0.65 inch of circumference. I know I can't just add it together.

I've found some archived thread with similar question, which included someone doing some "calculate the area of the hair in each, and add them together" thingy. I tried to do that with some on-line calculator and got area = 0.873, but I can't seem to get circumference from that.
As you can see I suck at math, so some help from someone that actually knows what all that means would be highly appreciated.;)

robin000
October 5th, 2013, 10:53 AM
You were almost there. Then you just take the square root of your total area divided by pi to get the radius [so sqrt(A/pi)=radius] and then multiply it by 2pi to get the new circumference. Which should be 3.314 I think.

robin000
October 5th, 2013, 11:19 AM
I guess I should also mention that the quickest way to find total circumference is:

Total Circumference = sqrt( (Circumference 1)^2 + (Circumference 2)^2 )

Vampyria
October 5th, 2013, 11:49 AM
Thank you! I tried it in that second way, and yes I get 3.314. :) Oh well, I hoped it would be a bit more. ;)

robin000
October 5th, 2013, 12:58 PM
You're welcome!

sweetinlace
October 6th, 2013, 10:45 AM
Why can't you just add them together? Totally thought that's how you did it.

Audhumla
October 6th, 2013, 05:07 PM
Why can't you just add them together? Totally thought that's how you did it.
You can't add them together because the circumference is just pi times the diameter so adding the circumferences is the same as adding the diameters and you can see if you just add them (in the picture the larger circle has a circumference equal to the sum of the circumferences of the smaller circles and a diameter equal to the sum of the smaller diameters) that you could fit a lot more hair in the larger circle than the smaller ones put together.
http://media-cache-ak0.pinimg.com/736x/d3/a1/d6/d3a1d6fc911530baaadfe1ee4f5145d8.jpg

The area within a circle which is equivalent to how much hair the pony can hold in this case is proportional to the radius squared. (area of a circle= pi x the radius squared)
Because you can multiply the radius by a scalar quantity (just a number with no variables) to get the circumference then the area within a circle or how much hair it can hold must be proportional to the circumference squared and not the circumference by itself. So you have to square the circumferences you're adding, add them and then take the square root of the answer. It gives a much different answer than just adding the circumferences.
eg. 3+5 = 8 but √(3+5) = ~6

sweetinlace
October 6th, 2013, 07:17 PM
Wow! That's very mathematical. I've got the math, and I'm pretty sure I get the concept. I haven't had to use my brain like that in years. Thank you for the explanation.