Đáp án+Giải thích các bước giải:

 $$
V_{\text{hộp}} = 5 \cdot 2 \cdot h = 10h
$$

$$
V_{1} = \pi r^2 h = \pi \cdot (0.5)^2 \cdot h = 0.25\pi h
$$

$$
V_{8} = 8 \cdot 0.25\pi h = 2\pi h
$$

$$
V_{\text{rỗng}} = 10h - 2\pi h
$$

$$
\frac{V_{\text{rỗng}}}{V_{\text{hộp}}} \cdot 100\%
= \frac{10h - 2\pi h}{10h} \cdot 100\%
= (1 - 0.2\pi)\cdot 100\%
$$

$$
(1 - 0.2 \cdot 3.14)\cdot 100\% = 37.2\%
$$

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