Evaluate
\frac{81\pi }{4}\approx 63.617251235
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4\pi \times \frac{81}{16}
Calculate \frac{9}{4} to the power of 2 and get \frac{81}{16}.
\frac{4\times 81}{16}\pi
Express 4\times \frac{81}{16} as a single fraction.
\frac{324}{16}\pi
Multiply 4 and 81 to get 324.
\frac{81}{4}\pi
Reduce the fraction \frac{324}{16} to lowest terms by extracting and canceling out 4.
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