right-angled triangle is formed with 72cm long iron wire. The ratio of the three sides is 3:4:5. What is the area of this triangle?
用72cm长的铁丝围成一个直角三角形，三边之比为3：4：5，这个三角形的面积是多少？
<gadget id="calculator">3 + 4 + 5</gadget>
<output>12</output>

<gadget id="calculator">3 / 12</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">72 * (1/4)</gadget>
<output>18</output>

<gadget id="calculator">4 / 12</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">72 * (1/3)</gadget>
<output>24</output>

<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<gadget id="calculator">18 * 12</gadget>
<output>216</output>

<result>216</result>