A rectangular parallelepiped swimming pool is 50m long, 20m wide, and 2m deep. A layer of cement needs to be applied around and on the bottom of the pool. It needs 3 kilograms of cement per square meter. How much cement is needed?
一个长方体的游泳池长50m宽20m深2m，要在四周和池底抹一层水泥，每平方米需要3千克水泥，需要多少水泥？
<gadget id="calculator">50 * 20</gadget>
<output>1_000</output>

<gadget id="calculator">50 * 2</gadget>
<output>100</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">100 + 40</gadget>
<output>140</output>

<gadget id="calculator">140 * 2</gadget>
<output>280</output>

<gadget id="calculator">1_000 + 280</gadget>
<output>1_280</output>

<gadget id="calculator">1_280 * 3</gadget>
<output>3_840</output>

<result>3_840</result>