A triangular billboard with a base length of 20.5m and a height of 5.6m. If you want to paint this billboard, you need to use 0.5 kilograms of paint per square meter, how many kilograms of paint should you prepare at least?
一块三角形的广告牌，底边长20.5m，高5.6m．如果要粉刷这块广告牌，每平方米用油漆0.5千克，至少要准备多少千克油漆？
<gadget id="calculator">5.6 / 2</gadget>
<output>2.8</output>

<gadget id="calculator">20.5 * 2.8 * 2 * 0.5</gadget>
<output>57.4</output>

<result>57.4</result>