Evaluate
21\sqrt{7}\approx 55.560777532
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7\sqrt{3}\sqrt{3}\sqrt{7}
Factor 21=3\times 7. Rewrite the square root of the product \sqrt{3\times 7} as the product of square roots \sqrt{3}\sqrt{7}.
7\times 3\sqrt{7}
Multiply \sqrt{3} and \sqrt{3} to get 3.
21\sqrt{7}
Multiply 7 and 3 to get 21.
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