There is a semicircular green space with a radius of 15m in a residential area. What is the perimeter of this green space?
某小区有一片半径为15m的半圆形绿地，这片绿地的周长是多少？
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 15 * 1</gadget>
<output>47.1</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">47.1 + 30</gadget>
<output>77.1</output>

<result>77.1</result>