A square vegetable field has a side length of 15 meters, and (2/5) of it is used to grow cabbage. What is the planting area of cabbage in square meters?
一个正方形的菜地，边长是15米，用其中的(2/5)种白菜，白菜的种植面积是多少平方米？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">15 * 15 * (2/5)</gadget>
<output>90</output>

<result>90</result>