Answer
$n\approx494$.
Work Step by Step
If the margin of error is $\pm4.5\%$, then our equation is: $\pm\frac{1}{\sqrt n}\cdot 100\%=\pm4.5\%=\pm0.045\\\frac{1}{\sqrt n}=0.045\\22.22\approx\sqrt{n}\\n\approx494$.
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