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I solved this.$$πr^2/r=π r$$In my book, they said it can not be determined. Am I right or wrong?
1 Answer
$\begingroup$For a circle of radius $r$, you are correct that the ratio is $\pi r$.
I suppose it's possible that the book means "which one of these four choices is correct cannot be determined without knowing $r$, because if $r$ happens to be $2$, then both answers "a" and "b" are correct, while if $r = \pi$, then both answers "a" and "c" are correct," or maybe they are saying it's $\pi r$ only if you know the radius of the circle is $r$, which wasn't stated explicitly, etc.
Either way, I might start searching for a new book, because one with wrong answers, or "trick-question" answers is probably not a good tool for learning mathematics.
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