Two concentric circles of different sizes, the radius of the outer circle is 5cm, the diameter of the inner circle is 6cm, what is the area of the circle in cm**2.
大小不等的两个同心圆，外圆半径是5cm，内圆直径是6cm，圆环的面积是多少cm**2．
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<gadget id="calculator">78.5 - 28.26</gadget>
<output>50.24</output>

<result>50.24</result>