Question

一个白色圆柱形筒仓直径为 $30$ 英尺，高为 $80$ 英尺。如图，筒仓上涂了一条水平宽度为 $3$ 英尺的红色条纹，绕筒仓完整转了两圈。条纹面积是多少平方英尺？

A white cylindrical silo has a diameter of $30$ feet and a height of $80$ feet. A red stripe with a horizontal width of $3$ feet is painted on the silo, as shown, making two complete revolutions around it. What is the area of the stripe in square feet?

$120$

$180$

$240$

$360$

$480$

答案：C

知识点：圆柱展开图（立体几何）平行四边形

难度评级：1600

小提示：

想象把筒仓上的条纹剪下并展开成平面图形。

Imagine cutting the stripe from the silo and unrolling it flat

大提示：

它会变成一个水平宽度为 $3$ 、高为 $80$ 的平行四边形。

It becomes a parallelogram with horizontal width $3$ and height $80$

解答：

将条纹展开后，它成为一个平行四边形。其底边（水平宽度）为 $3$ 英尺，高跨过整个筒仓，为 $80$ 英尺。

因此面积为 $3 \times 80 = 240$ 平方英尺。

所以正确答案是 C。

Unrolling the stripe flattens it into a parallelogram. Its base (the horizontal width) is $3$ feet and its height spans the full $80$ feet of the silo.

The area is therefore $3 \times 80 = 240$ square feet.

Thus, the correct answer is C.

2004 AMC 10A 第 19 题

答案：C

难度评级：1600

小提示：

大提示：

解答：

其他年份的第 19 题