It is known that a sheet of iron is 25.12 cm long and 18.84 cm wide. Coupled with a circular iron plate with d = how many centimeters, it can be made into a cylinder without a cover.
已知一块铁皮长25.12厘米，宽18.84厘米．配上一块d=多少厘米的圆形铁板，可以做成一个无盖的圆柱体．
<gadget id="calculator">25.12 / 3.14 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<result>8</result>