Question

如图，七个单位立方体拼成一个立体图形。体积的立方单位数与表面积的平方单位数之比是多少？

A shape is created by joining seven unit cubes, as shown. What is the ratio of the volume in cubic units to the surface area in square units?

$\:1 : 6$

$\: 7 : 36$

$\: 1 : 5$

$\: 7 : 30$

$\: 6 : 25$

这个立体由 $7$ 个单位立方体组成，所以体积是 $7$ 立方单位。

中央立方体没有外露面。六个外侧立方体各有 $5$ 个外露面，所以表面积为 $6\cdot5=30$ 平方单位。

体积与表面积之比为 $7:30$ 。

所以正确答案是 D。

The shape uses $7$ unit cubes, so its volume is $7$ cubic units.

The center cube has no exposed faces. Each of the six outer cubes has $5$ exposed faces, for a total surface area of $6\cdot5=30$ square units.

The ratio of volume to surface area is $7:30$ .

Thus, D is the correct answer.