A billboard is a triangle with a base of 12.5 meters and a height of 6.4 meters. If you want to paint the billboard (paint one side first), use 0.4 kilograms of paint per square meter, how many kilograms of paint do you need to paint this billboard?
一块广告牌是三角形，底是12.5米，高6.4米．如果要给广告牌刷漆(先刷一面)每平方米用油漆0.4千克，刷这个广告牌需要油漆多少千克？
<gadget id="calculator">6.4 / 2</gadget>
<output>3.2</output>

<gadget id="calculator">12.5 * 3.2</gadget>
<output>40</output>

<gadget id="calculator">40 * 0.4</gadget>
<output>16</output>

<result>16</result>