Answer
$$\frac{4}{\sqrt{20}}=\frac{2\sqrt{5}}{5}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}\frac{4}{\sqrt{20}}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}} \frac{ 4 }{\sqrt{ 20 }} \times \frac{ \color{orangered}{\sqrt{ 20 }} }{ \color{orangered}{\sqrt{ 20 }}} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{4\sqrt{20}}{20} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}} \frac{ 4 \sqrt{ 4 \cdot 5 }}{ 20 } \xlongequal{ } \\[1 em] & \xlongequal{ } \frac{ 4 \cdot 2 \sqrt{ 5 } }{ 20 } \xlongequal{ } \\[1 em] & \xlongequal{ }\frac{8\sqrt{5}}{20} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle4}{\textcircled {4}} } }}} \frac{ 8 \sqrt{ 5 } : \color{blue}{ 4 } }{ 20 : \color{blue}{ 4 } } \xlongequal{ } \\[1 em] & \xlongequal{ }\frac{2\sqrt{5}}{5}\end{aligned} $$ | |
| ① | Multiply both top and bottom by $ \color{orangered}{ \sqrt{ 20 }}$. |
| ② | In denominator we have $ \sqrt{ 20 } \cdot \sqrt{ 20 } = 20 $. |
| ③ | Simplify $ \sqrt{ 20 } $. |
| ④ | Divide both the top and bottom numbers by $ \color{blue}{ 4 }$. |
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