After a triangle is reduced by 1:3, the area of the reduced triangle is the same as the area of the original triangle.
一个三角形按1：3缩小后，那么缩小后的三角形面积是原三角形面积的多少．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">1 * 1 * (1/2)</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/3) * (1/3) * 1</gadget>
<output>1/9 = around 0.111111</output>

<result>1/9 = around 0.111111</result>