The perimeter of an equilateral triangle is 30 meters, the height is the base (4/5), what is the area of the triangle in square meters?
一个等边三角形的周长是30米，高是底的(4/5)，这个三角形的面积是多少平方米．
<gadget id="calculator">30 / 3</gadget>
<output>10</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">10 * (4/5)</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<result>40</result>