There is a cube water tank with a side length of 9 decimeters. After it is filled with water, it is poured into a cuboid water tank. The water depth is measured to be 30 cm. What is the area of the bottom of this cuboid water tank?
有一个棱长是9分米的正方体水箱，装满水后，倒入一个长方体水箱内，量得水深30厘米，这个长方体水箱的底面积是多少平方分米？
<gadget id="calculator">30 / 10</gadget>
<output>3</output>

<gadget id="calculator">9 / 3</gadget>
<output>3</output>

<gadget id="calculator">9 * 9 * 3</gadget>
<output>243</output>

<result>243</result>