The perimeter of a semicircular piece of paper is 10.28 decimeters, what is its radius?
半圆形纸片的周长是10.28分米，它的半径是多少．
<gadget id="calculator">3.14 + 2</gadget>
<output>5.14</output>

<gadget id="calculator">10.28 / 5.14</gadget>
<output>2</output>

<result>2</result>