Evaluate
\frac{4\sqrt{5}}{5}\approx 1.788854382
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\frac{8}{\sqrt{20}}
Multiply 2 and 4 to get 8.
\frac{8}{2\sqrt{5}}
Factor 20=2^{2}\times 5. Rewrite the square root of the product \sqrt{2^{2}\times 5} as the product of square roots \sqrt{2^{2}}\sqrt{5}. Take the square root of 2^{2}.
\frac{8\sqrt{5}}{2\left(\sqrt{5}\right)^{2}}
Rationalize the denominator of \frac{8}{2\sqrt{5}} by multiplying numerator and denominator by \sqrt{5}.
\frac{8\sqrt{5}}{2\times 5}
The square of \sqrt{5} is 5.
\frac{4\sqrt{5}}{5}
Cancel out 2 in both numerator and denominator.
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