A classroom is 10 meters long, 7 meters wide, and 3 meters high. The ceiling and four walls of the classroom need to be painted, and the area of the classroom is 20 square meters excluding doors, windows and blackboards. If 0.25 kilograms of paint is used per square meter, how many kilograms of paint are needed in total?
一间教室长10米，宽7米，高3米，要粉刷教室的天花板和四面墙壁，除去门窗和黑板的面积20平方米，如果每平方米用涂料0.25千克，一共需要涂料多少千克？
<gadget id="calculator">10 * 7</gadget>
<output>70</output>

<gadget id="calculator">10 * 3 * 2</gadget>
<output>60</output>

<gadget id="calculator">7 * 3 * 2</gadget>
<output>42</output>

<gadget id="calculator">42 - 20</gadget>
<output>22</output>

<gadget id="calculator">70 + 60 + 22</gadget>
<output>152</output>

<gadget id="calculator">152 * 0.25</gadget>
<output>38</output>

<result>38</result>