It is known that the circumference of a rectangle and a circle are equal. The length of the rectangle is 5 cm and the width is 2.85 cm. How many centimeters is the semilongitude of the circle?
已知一个长方形和一个圆的周长相等，这的长方形的长是5厘米，宽是2.85厘米，那么这个圆的半经是多少厘米？
<gadget id="calculator">5 + 2.85</gadget>
<output>7.85</output>

<gadget id="calculator">2 / 3.14 / 2</gadget>
<output>0.318471</output>

<gadget id="calculator">7.85 * 0.318471</gadget>
<output>2.499997</output>

<result>2.499997</result>