In a cuboid tank with a length of 15 cm, a width of 9 cm, and a height of 6 cm, pour 540 ml of water. How deep is the water in the tank?
在一个长是15厘米，宽是9厘米，高是6厘米的长方体水缸里，倒入540毫升的水，水缸里的水有多深？
<gadget id="calculator">15 * 9</gadget>
<output>135</output>

<gadget id="calculator">540 / 135</gadget>
<output>4</output>

<result>4</result>