Evaluate
\frac{21\pi }{4}\approx 16.493361431
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\pi \times 6\times \frac{7}{8}
Divide 6 by \frac{8}{7} by multiplying 6 by the reciprocal of \frac{8}{7}.
\pi \times \frac{6\times 7}{8}
Express 6\times \frac{7}{8} as a single fraction.
\pi \times \frac{42}{8}
Multiply 6 and 7 to get 42.
\pi \times \frac{21}{4}
Reduce the fraction \frac{42}{8} to lowest terms by extracting and canceling out 2.
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