The radius of the bottom of a cylinder is 10 cm, and the height is 20 cm. Divide the bottom of the cylinder into many equal small sectors, cut them, and assemble them into an approximate cuboid. What is the length of the cuboid in centimeters?
一个圆柱的底面半径是10厘米，高是20厘米，把它的底面分成许多相等的小扇形，切开，拼成一个近似的长方体，长方体的长是多少厘米．
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 10 * 1</gadget>
<output>31.4</output>

<result>31.4</result>