The base of a triangle is 15 cm and the height is twice the base. What is the area of the triangle?
一个三角形的底是15cm，高是底的2倍，这个三角形的面积是多少．
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">15 * 15</gadget>
<output>225</output>

<result>225</result>