If an 8-meter-long horse rope is extended by 1 meter, how much more grass can the horse eat?
如果将一根8米长的拴马绳子加长1米，马儿可多吃多大面积的草？
<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">8 ** 2</gadget>
<output>64</output>

<gadget id="calculator">81 - 64</gadget>
<output>17</output>

<gadget id="calculator">3.14 * 17</gadget>
<output>53.38</output>

<result>53.38</result>