Question: Sort the cards into three groups.
Equivalent to $2\sqrt{5}$
Neither
Equivalent to $5$
$\sqrt{2} \cdot \sqrt{5}$
$\sqrt{2} \cdot \sqrt{2} \cdot \sqrt{5}$
$\sqrt{25}$
$\sqrt{4} \cdot \sqrt{5}$
$\sqrt{20}$
$(\sqrt{5})^{2}$
1. **State the problem:** We need to sort the given expressions into three groups: those equivalent to $2\sqrt{5}$, those equivalent to $5$, and those that are neither.
2. **Recall important formulas:**
- $\sqrt{a} \cdot \sqrt{b} = \sqrt{ab}$
- $(\sqrt{a})^{2} = a$
3. **Evaluate each expression:**
- $\sqrt{2} \cdot \sqrt{5} = \sqrt{2 \times 5} = \sqrt{10}$ (Neither)
- $\sqrt{2} \cdot \sqrt{2} \cdot \sqrt{5} = (\sqrt{2} \cdot \sqrt{2}) \cdot \sqrt{5} = \sqrt{4} \cdot \sqrt{5} = 2 \sqrt{5}$ (Equivalent to $2\sqrt{5}$)
- $\sqrt{25} = 5$ (Equivalent to $5$)
- $\sqrt{4} \cdot \sqrt{5} = \sqrt{4 \times 5} = \sqrt{20} = 2 \sqrt{5}$ (Equivalent to $2\sqrt{5}$)
- $\sqrt{20} = \sqrt{4 \times 5} = 2 \sqrt{5}$ (Equivalent to $2\sqrt{5}$)
- $(\sqrt{5})^{2} = 5$ (Equivalent to $5$)
4. **Sort the cards:**
- Equivalent to $2\sqrt{5}$: $\sqrt{2} \cdot \sqrt{2} \cdot \sqrt{5}$, $\sqrt{4} \cdot \sqrt{5}$, $\sqrt{20}$
- Equivalent to $5$: $\sqrt{25}$, $(\sqrt{5})^{2}$
- Neither: $\sqrt{2} \cdot \sqrt{5}$
**Final answer:**
- $2\sqrt{5}$ group: $\sqrt{2} \cdot \sqrt{2} \cdot \sqrt{5}$, $\sqrt{4} \cdot \sqrt{5}$, $\sqrt{20}$
- $5$ group: $\sqrt{25}$, $(\sqrt{5})^{2}$
- Neither group: $\sqrt{2} \cdot \sqrt{5}$