There is a rectangular watermelon field with a length of 7m and a width of 4m. It can harvest an average of 35 kilograms of watermelons per square meter. How many kilograms of watermelons can be harvested in this field?
有一块长方形西瓜地，长7m，宽4m，每平方米平均可收西瓜35千克，这块地一共可收西瓜多少千克？
<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<gadget id="calculator">28 * 35</gadget>
<output>980</output>

<result>980</result>