The area of a square farmland is 1 hectare. Later, the side length of this piece of farmland doubled, how many hectares did the area increase?
一块正方形的农田的面积是1公顷，后来这片农田的边长增加了一倍，面积增加了多少公顷．
<gadget id="calculator">100 + 100</gadget>
<output>200</output>

<gadget id="calculator">200 / 10_000</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">200 * (1/50)</gadget>
<output>4</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<result>3</result>