If three cylindrical steel materials with a base diameter of 4 cm are welded into a steel pipe, the surface area will be reduced by how many square centimeters.
把3根底面直径是4厘米的圆柱形钢材焊接成一根钢管，它的表面积减少多少平方厘米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 4</gadget>
<output>50.24</output>

<result>50.24</result>