Change a rectangular coil with a width of 10 meters and a length twice its width into a square. What is the side length of this square in meters?
将一个宽为10米，长是宽2倍的长方形线圈改成一个正方形，这个正方形边长是多少米？
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 * (1/2)</gadget>
<output>15</output>

<result>15</result>