Uncle Liu surrounded a semicircular vegetable field with a diameter of 3 meters against the wall. How many meters of fence are needed to surround the vegetable field.
刘大爷靠墙围了一个直径是3米的半圆菜地，围菜地需要多少米的篱笆．
<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">3.14 * (3/2)</gadget>
<output>4.71</output>

<gadget id="calculator">4.71 + 3</gadget>
<output>7.71</output>

<result>7.71</result>