If a cuboid wood has a cross-sectional area of 9㎡, if it is cut into two sections, how much will the surface area increase in m**2.
一根长方体木料，它的横截面积是9㎡，把它截成2段，表面积增加多少m**2．
<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>