What is the circumference of a semicircular object with a radius of 15 cm?
一个半圆形零件，半径是15厘米，它的周长是多少厘米．
<gadget id="calculator">3.14 * 15</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>