The perimeter of a semicircular lawn is 128.5m, how many square meters does this lawn occupy? (Hint: The circumference of a semicircle is πr+2r=r(π+2).)
一个半圆形草坪的周长是128.5m，这个草坪的占地面积是多少平方米？(提示：半圆周长为πr+2r=r(π+2)．)
<gadget id="calculator">50 / 2</gadget>
<output>25</output>

<gadget id="calculator">25 ** 2</gadget>
<output>625</output>

<gadget id="calculator">625 / 2</gadget>
<output>625/2 = around 312.5</output>

<gadget id="calculator">3.14 * (625/2)</gadget>
<output>981.25</output>

<result>981.25</result>