Cut a line segment of 3 cm and 7 cm from the vertex on both sides of an angle, and draw a parallelogram on the basis of these two line segments. Calculate the perimeter of the parallelogram in centimeters.
在一个角的两边从顶点开始分别截取3厘米和7厘米的线段，再在这两条线段的基础上补画成一个平行四边形．最后算出平行四边形的周长是多少厘米．
<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<result>20</result>