Use a 30cm long iron wire to weld a cube (no remaining iron wire), what is its surface area in cm**2.
用一根长30cm的铁丝焊一个正方体(没有剩余铁丝)，它的表面积是多少cm**2．
<gadget id="calculator">30 / 12</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">(5/2) * (5/2) * 6</gadget>
<output>75/2 = around 37.5</output>

<result>75/2 = around 37.5</result>