A cow is tied to a stake in the grass. The length of the rope is 5 meters. If the rope is lengthened by 2 meters, how many square meters of grass can the cow eat at most?
一头牛拴在草地里的木桩上，绳子的长度是5米，现将绳子加长2米，这头牛最多可以吃到多少平方米的草？
<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">3.14 * 49</gadget>
<output>153.86</output>

<result>153.86</result>