# What's the perimeter of a sphere?

Say the perimeter of a unit cube is 12, because that's the sum of all its edges, hence it's the cube's perimeter.

What would it be for a sphere of any proportion?

Note by Tim Ye
5 years, 2 months ago

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We don't call the sum of the edge lengths of a polyhedron its "perimeter." A perimeter is the boundary of a two-dimensional figure.

Because a sphere has no edges, it has no such sum as you have defined with the cube. Your question is analogous to asking for the number of vertices of a circle. There is none.

- 5 years, 2 months ago

I interpret it as the sum of edges of a solid by your example of a cube. But a sphere has no edges, so the 'perimeter' is 0. If you are talking about adding all those tiny circumferences of the sphere up, you end up integrating them into the surface area of the sphere, $$4\pi r^2$$.

- 5 years, 2 months ago

Correct.

- 5 years, 2 months ago

Well you're just too smart for a 14 year old. I think that is kinda the answer.

- 5 years, 2 months ago

Tim Y. has already defined a "perimeter" of a 3D solid to be the sum of its edges. It is on our part, and not his, to understand what is implied.

- 5 years, 2 months ago

- 5 years, 2 months ago

We define perimeter for 2-dimensional figures only.

- 5 years, 2 months ago

i don't think it has a perimeter......as it is a 3D figure........

- 5 years, 2 months ago

bebzz.... see figure chaiye 3D ho yah 2D ....hum haar time perimeter find kaar sakte hai because vo humesha hi line segments se banni hoti hai .... and the figures with curves ,,hum unka circumfrence find kaar sakte hai ...."CIRCUMFRENCE" ......................remember hum circle ka circumfrence find karte thei......... same way sphere ka bhi circumfrence nikkal sakta hai.

- 5 years, 2 months ago

srry cant read hindi lol XD

- 5 years, 2 months ago

AND I would like to say one more thing.....next time dont...put ur silly...comments...in hindi.....

- 5 years, 2 months ago

It's same as that of a CIRCLE .......... 2pi R = circumfrence

- 5 years, 2 months ago

You cannot find the circumference of a sphere as such but you can find the circumference of the circles in it.

- 5 years, 2 months ago

- 5 years, 2 months ago

U are wrong,think of a sphere like a figure made of many circles of various sizes,the biggest being at the center,and decreasing gradually.what u said wouldn't make sense now would it?

- 5 years, 2 months ago

ohhh i guess you aren't familiar...with sphere and its properties....it cant be 2pi R

- 5 years, 2 months ago

I DON'T THINK SO .......

- 5 years, 2 months ago

BUT I THINK SO.....AND BEFORE WRITING ANYTHING.....THINK OVER IT.......it will involve a typical integration with limits..... i think BK MAESTER T...is right.....

- 5 years, 2 months ago

ohk.....toh aap meko sphere ka " CIRCUMFERENCE " find karke do.....plzzzzz........woh bhi curve hai na........? :/

[ i said
fine! if is it so...then find "CIRCUMFERENCE" of...sphere since its a curve tooo....]
as u quoted "and the figures with curves ,,hum unka circumfrence find kaar sakte hai ...."CIRCUMFRENCE" same way sphere ka bhi circumfrence nikkal sakta hai. "

aur jab ho jae toh btana....me yahi milungi....except for the condition ki tum use kisise pucho ya fir koi search engine khol kar uspe se copy...paste karo.....huh....

[ i said when u'll finish that....post it here i'll be here only.....and terms and conditions for u.....DONT ASK IT FROM SOMEONE AND DONT CHEAT IT FROM SOME SEARCH ENGINE.....OK...]

- 5 years, 2 months ago

probably undefined since there are no edges on a sphere

- 5 years, 2 months ago

Well, going by your definition, lets say the sphere has infinite sides, then Perimeter = (infinity) x (whatever is the value of each side) p = ∞ But wait, the length of each side is zero as they are just points. ∴ p = ∞ x 0 = 1 (if you can consider that as true) Hence your answer is 1.

- 5 years, 2 months ago

Perimeter doesn't apply to 3 dimensional figures. It is the boundary of a 2 dimensional figure.Since, 3 dimensional figures don't have any boundary , so, neither a sphere nor a cube has a perimeter.

- 5 years, 2 months ago

Guyss.... first of all , cube is also a 3D figure and In the figures like that of a circle or a sphere ,we don't take perimeter ,there it's circumfrence . And in sphere we can have the circumfrence .. agree?

- 5 years, 2 months ago