A rectangular test field is 42 meters long and half the width. If 9 kilograms of vegetables are harvested per square meter, how many kilograms of vegetables can be harvested in this test field?
一块长方形试验田，长是42米，宽是长的一半，如果每平方米收青菜9千克，这块试验田一共能收多少千克的青菜？
<gadget id="calculator">42 / 2</gadget>
<output>21</output>

<gadget id="calculator">42 * 21 * 9</gadget>
<output>7_938</output>

<result>7_938</result>