A triangular billboard has a base length of 15m and a height of 8.4m. If the billboard is to be painted with paint, the amount of paint used per square meter is 0.75 kg. How much paint should be used for this billboard?
一块三角形广告牌，底长15m，高8.4m，如果要用油漆刷这块广告牌，每平方米用油漆0.75千克，这块广告牌要用油漆多少千克？
<gadget id="calculator">8.4 / 2</gadget>
<output>4.2</output>

<gadget id="calculator">15 * 4.2 * 0.75</gadget>
<output>47.25</output>

<result>47.25</result>