The circular scissors form an approximate rectangle. The width of this rectangle is 10 decimeters. Then, what is the length of this rectangle in decimeters.
圆剪拼成一个近似的长方形，这个长方形的宽是10分米，那么，这个长方形的长是多少分米．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<result>31.4</result>