The cross-section of a cuboid is 15 square decimeters, if it is cut into 4 sections, how many square decimeters will the surface area increase?
一个长方体的横截面是15平方分米，把它横截成4段，表面积增加多少平方分米．
<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<result>90</result>