A triangular billboard with a base of 25 decimeters and a height of 20 decimeters. If 2 kilograms of paint are painted per square meter, how much paint is needed to paint the front and back sides of this billboard?
三角形广告牌，底25分米，高20分米．如果每平方米刷漆2千克，那么将这个广告牌正反两面刷漆，需要多少油漆？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">2 / 100</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">25 * 10 * (1/50) * 2</gadget>
<output>10</output>

<result>10</result>