How do you find the cicumference when you know the diameter?

Answer 1

Multiply the diameter by (pi) to get the circumference.

(Pi) is a number that can never be written exactly.

Here it is with only the first 15 decimal places: 3.14159 26535 89792

You can never calculate exactly the correct answer, but you can get as close

to it as you want by using more decimal places of (pi).

From, time to time, you'll see orgies of numbers, on this and other websites,

where people will write out (pi) with a hundred or a thousand decimal places.

Mathematicians in Japan, using parallel supercomputers, have calculated it

out to 4 trillion decimal places.

But if you just use 3.142 then your answer is within 0.02% of the exact answer,

so you can see that there's hardly ever any need for more than that.

Another handy, approximate number for (pi) that's easy to use is 22/7 . If you use that,

then the answer you get is within about 0.04% of the real answer. Pretty good.