The sports center builds a rectangular swimming pool with a length of 50 meters, a width of 15 meters and a depth of 1.8 meters. The walls and bottom of the swimming pool should be paved with tiles. If about 20 tiles are used per square meter, how many tiles are needed for this swimming pool?
体育中心建造一个长方形的游泳池，长50米，宽15米，深1.8米，要在游泳池的四壁和底面铺切瓷砖．如果每平方米大约用20块瓷砖，这个游泳池共需要瓷砖多少块？
<gadget id="calculator">50 * 15</gadget>
<output>750</output>

<gadget id="calculator">50 * 1.5 * 2</gadget>
<output>150</output>

<gadget id="calculator">15 * 1.5 * 2</gadget>
<output>45</output>

<gadget id="calculator">750 + 150 + 45</gadget>
<output>945</output>

<gadget id="calculator">20 * 945</gadget>
<output>18_900</output>

<result>18_900</result>