Pour 15 cubic decimeters of water into a tank with a length of 5 decimeters, a width of 3 decimeters, and a height of 4 decimeters. What is the distance in decimeters from the water surface to the mouth of the tank?
把15立方分米的水倒入一个长5分米、宽3分米、高4分米的水槽中，求水面到水槽口的距离是多少分米？
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">15 / 15</gadget>
<output>1</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<result>3</result>