cuboid glass container can hold up to 420ml of water, and the height of the container is 3dm. What is the area of its bottom in dm**2.
一个长方体的玻璃容器最多可装水420ml，容器高3dm，它的底面积是多少dm**2．
<gadget id="calculator">420 / 1_000</gadget>
<output>21/50 = around 0.42</output>

<gadget id="calculator">(21/50) / 3</gadget>
<output>7/50 = around 0.14</output>

<result>7/50 = around 0.14</result>