The formula for the circumference of a circle is cap c is equal to pi d , where d is the length of the diameter. If d is a rational number, what can you conclude about the circumference?

The circumference is C = πd. Since π is irrational, multiplying it by a nonzero rational diameter gives an irrational number. So the circumference is irrational (choice A). If the diameter were zero, the circumference would be 0, but a circle’s diameter is positive.

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