cuboid fish tank, measured from the inside, has a length of 5 decimeters, a width of 3 decimeters, and a height of 4 decimeters. Now pour 54 liters of water into the fish tank. How many decimeters is the water surface from the edge of the fish tank?
一个长方体鱼缸，从里面量，长5分米，宽3分米，高4分米，现在往鱼缸注入54升水，水面离鱼缸的沿口有多少分米？
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">54 / 15</gadget>
<output>18/5 = around 3.6</output>

<gadget id="calculator">4 - (18/5)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>