A trapezoidal billboard with an upper base of 8 meters, a lower base of 10 meters, and a height of 5 meters. How many kilograms of paint is needed to paint the front and back sides of this billboard? (1 kg of paint is required per square meter)
一块梯形的宣传牌，上底8米，下底10米，高5米．油漆这块宣传牌的正反两面共需油漆多少千克？(每平方米需用油漆1千克)
<gadget id="calculator">8 + 10</gadget>
<output>18</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">18 * (5/2) * 2 * 1</gadget>
<output>90</output>

<result>90</result>