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find the circumferance of a circle that has a diameter of three inches. Give exact value

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3 Answers

circumference=pi*diameter
C=(pi)(d)
  =3.14159*3
  =9.42477 in
this is not an exact value because pi is an irrational number, a non-ending, non-repeating decimal,
in other words, it cannot be written as a simple fraction a/b
Circumference = pi(D) = (pi)(3) = 3pi or 3π. That's the EXACT value.

Approximate value would be using 3.14 for pi
3.14
x 3
====
9.42 in.
What is wrong with 3π as an exact answer?  I admit it is not possible to write it as a decimal, but that was not the question.

Comments

C=3pi as an answer seems too easy for a homework problem. Secondly, the word exact may have different meanings for different people. Maybe to the student exact meant 3 times some approximate value of pi. Or maybe 3pi is what the student was looking for. Anyway, we gave him both answers to choose from.

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