The outer radius of a ring is 8 decimeters, and the inner radius is 5 decimeters. Find the area of the ring?
一个环形的外圆半径是8分米，内圆半径5分米，求环形的面积？
<gadget id="calculator">8 ** 2</gadget>
<output>64</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">64 - 25</gadget>
<output>39</output>

<gadget id="calculator">3.14 * 39</gadget>
<output>122.46</output>

<result>122.46</result>