A classroom is 8 meters long, 6 meters wide, and 4 meters high. Now its walls and ceiling need to be painted, and the doors, windows and blackboards are deducted for a total of 20 square meters. If 0.5 kg of paint is used per square meter, how many kilograms of paint are needed in total?
一间教室长8米，宽6米，高4米，现在要粉刷它的四壁和天花板，扣除门窗和黑板共20平方米．如果每平方米用涂料0.5千克，一共需要多少千克涂料？
<gadget id="calculator">8 * 6</gadget>
<output>48</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">6 * 4</gadget>
<output>24</output>

<gadget id="calculator">48 + 32 + 24</gadget>
<output>104</output>

<gadget id="calculator">104 * 2</gadget>
<output>208</output>

<gadget id="calculator">208 - 48 - 20</gadget>
<output>140</output>

<gadget id="calculator">140 * 0.5</gadget>
<output>70</output>

<result>70</result>