How many lawns are needed to lay a lawn with a side length of 20 meters on a piece of land with a length of 4 kilometers and a width of 3 kilometers?
在一块长4千米，宽3千米的土地上铺边长为20米的草坪，需要多少块这样的草坪？
<gadget id="calculator">4 * 1_000</gadget>
<output>4_000</output>

<gadget id="calculator">3 * 1_000</gadget>
<output>3_000</output>

<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<gadget id="calculator">3_000 / 400</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">4_000 * (15/2)</gadget>
<output>30_000</output>

<result>30_000</result>