After putting the cylinders together into an approximate cuboid, the surface area increases by 40cm**2. If the height of the cylinder is 5cm, what is the volume of the cuboid dm**3.
把圆柱拼成近似的长方体后表面积增加40cm**2，若圆柱的高是5cm，则长方体的体积是多少dm**3．
<gadget id="calculator">40 / 2 / 5</gadget>
<output>4</output>

<gadget id="calculator">5 / 1_000</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">4 * 4 * 3.14 * (1/200)</gadget>
<output>0.2512</output>

<result>0.2512</result>