A cylinder (joints are not counted) is surrounded by a rectangular piece of paper 9 cm long and 4 cm wide. What is the lateral area of this cylinder in square centimeters?
用一个长9厘米，宽4厘米的长方形纸片围成一个圆柱(接头不计)，这个圆柱的侧面积是多少平方厘米．
<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>