There is an old apricot tree in the botanical garden. Use a 4m long tape measure to measure the circumference of its trunk. The tape measure is still 0.86m after two weeks on the apricot tree. What is the radius of the trunk of this apricot tree in centimeters?
植物园有一棵古老的杏树，用4m长的卷尺去测它的树干周长，这根卷尺在杏树上饶了两周后还有0.86m，这棵杏树树干的半径是多少厘米？
<gadget id="calculator">4 - 0.86</gadget>
<output>3.14</output>

<gadget id="calculator">3.14 / 2 / 3.14 / 2</gadget>
<output>0.25</output>

<gadget id="calculator">0.25 * 100</gadget>
<output>25</output>

<result>25</result>