A piece of square steel has a cross-section of a square with a side length of 3 cm and a length of 5 meters. The steel weighs 7.8 kg per square decimeter. How much does this square steel weigh?
一块方钢，横截面是边长3厘米的正方形，长5米，每平方分米钢重7.8千克，这根方钢重多少千克？
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">7.8 * (3/10) * (3/10) * 5 * 10</gadget>
<output>35.1</output>

<result>35.1</result>