The floor of Uncle Wang's house is a rectangle with a length of 6.9 decimeters and a width of 7.2 decimeters, because the floor tiles should be laid in time during the decoration, and there is no surplus. How many floor tiles are needed in total?
王叔叔家的地面是长6.9分米，宽7.2分米的长方形，因装修时要及时铺上地砖，且没有剩余．一共需要多少块地砖？
<gadget id="calculator">21 * 24</gadget>
<output>504</output>

<result>504</result>