Problem: Multiply $6\sqrt{5}$ by $2\sqrt{5}$
Group the parts: Multiply the whole numbers together and the radicals together: $(6 \times 2) \times (\sqrt{5} \times \sqrt{5})$
Simplify: $12 \times 5$
Result: $60$
Problem: Multiply $2\sqrt{8}$ by $5\sqrt{2}$
Group the parts: Multiply whole numbers $(2 \times 5)$ and combine the radicals $\sqrt{8 \times 2}$
Multiply: $10\sqrt{16}$
Simplify the square root: Since $\sqrt{16} = 4$, the expression becomes $10(4)$
Result: $40$