There is a parallelogram steel plate with a base of 8.4 decimeters and a height of 3.5 decimeters. If the steel plate weighs 0.7 kg per square decimeter, how much does the steel plate weigh?
有一块平行四边形钢板，底是8.4分米，高是3.5分米．如果每平方分米钢板重0.7千克，这块钢板重多少千克？
<gadget id="calculator">8.4 * 3.5</gadget>
<output>29.4</output>

<gadget id="calculator">0.7 * 29.4</gadget>
<output>20.58</output>

<result>20.58</result>