A square steel is 3 meters long, and its cross-section is a square with a side length of 4 cm. It is known that the square steel weighs 7.8 kg per cubic decimeter. How much does this square steel weigh?
一根方钢长3米，它的横截面是一个边长为4厘米的正方形，已知每立方分米的方钢重7.8千克，这根方钢重多少千克？
<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">(2/5) * (2/5) * 30 * 7.8</gadget>
<output>37.44</output>

<result>37.44</result>