SOLUTION: What is the formula for finding the radius of a circle when you know the circumference?

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Question 3842: What is the formula for finding the radius of a circle when you know the circumference?
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
to do anything algebraically with square rooting a fraction, the numerator and denominator have to be good numbers...

sqrt%2816%2F25%29 is either +4/5 or -4/5

sqrt%289%2F20%29 is +3%2Fsqrt%2820%29 or -3%2Fsqrt%2820%29. You can leave this alone or you can "simplify" the square root...called a "surd" - make sure you spell this and more importantly, pronounce this, correctly.

sqrt%2820%29 is the same thing as sqrt%284%2A5%29 which is the same thing as sqrt%284%29sqrt%285%29, which is +-2sqrt%285%29.

Hope this helps

jon