The perimeter of a right triangle is 90 cm, and the ratio of the lengths of the three sides is 13:12:5, what is its area in square centimeters?
一个直角三角形的周长是90厘米，三条边长之比是13：12：5，它的面积是多少平方厘米．
<gadget id="calculator">13 + 12 + 5</gadget>
<output>30</output>

<gadget id="calculator">12 / 30</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">90 * (2/5)</gadget>
<output>36</output>

<gadget id="calculator">5 / 30</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">90 * (1/6)</gadget>
<output>15</output>

<gadget id="calculator">15 / 2</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">36 * (15/2)</gadget>
<output>270</output>

<result>270</result>