A room is 5 meters long and 4 meters wide. A 20-centimeter-thick layer of sand is placed in this room. The sand weighs 1.8 tons per cubic meter. How many tons of sand are needed in total?
一个房间长5米，宽4米，在这个房间里铺上20厘米厚的沙子，每立方米沙重1.8吨，共要多少吨沙？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">5 * 4 * (1/5) * 1.8</gadget>
<output>7.2</output>

<result>7.2</result>