On the campus of Rongxin Primary School, there is a square experimental field with a side length of 9 meters. The average harvest of potatoes per square meter is 1.5 kilograms. How many kilograms of potatoes are harvested in this experimental field?
榕欣小学校园里有一块边长9米的正方形试验田，平均每平方米收土豆1.5千克，这块试验田共收土豆多少千克？
<gadget id="calculator">9 * 9</gadget>
<output>81</output>

<gadget id="calculator">1.5 * 81</gadget>
<output>121.5</output>

<result>121.5</result>