To make 100 sections of cylindrical chimney, the diameter of its bottom surface is 10 cm, and the length of each section is 5 decimeters, at least how many square meters of iron sheets are needed.
做100节圆柱形烟筒，它的底面直径是10厘米，每节长5分米，至少需多少平方米铁皮．
<gadget id="calculator">3.14 * 10 * 5 * 10</gadget>
<output>1_570</output>

<gadget id="calculator">100 / 10_000</gadget>
<output>1/100 = around 0.01</output>

<gadget id="calculator">1_570 * (1/100)</gadget>
<output>157/10 = around 15.7</output>

<result>157/10 = around 15.7</result>