Paint a classroom with a length of 8 meters, a width of 6 meters, and a height of 4 meters. The area of doors, windows and blackboards is 25 square meters. If 0.5 kg of lime is used per square meter, how many kg of lime are needed in total?
粉刷一间长8米，宽6米，高4米的教室，门窗及黑板面积为25平方米．如果每平方米用石灰0.5千克，共需要多少千克石灰？
<gadget id="calculator">6 * 8</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">8 * 6</gadget>
<output>48</output>

<gadget id="calculator">208 - 48 - 25</gadget>
<output>135</output>

<gadget id="calculator">135 * 0.5</gadget>
<output>67.5</output>

<result>67.5</result>