The perimeter of a right triangle is 144 decimeters, and the length ratio of the three sides is 3:4:5. What is the area of this right triangle?
直角三角形的周长是144分米，三条边的长度比是3：4：5．这个直角三角形的面积是多少平方分米？
<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">144 * (1/4)</gadget>
<output>36</output>

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

<gadget id="calculator">144 * (1/3)</gadget>
<output>48</output>

<gadget id="calculator">48 / 2</gadget>
<output>24</output>

<gadget id="calculator">36 * 24</gadget>
<output>864</output>

<result>864</result>