A cuboid water tank is 40 cm long and 30 cm wide when measured from the inside, and the height of the water in the tank is 10 cm. After putting a cube with sides 20 cm long, the top surface of the iron block is still higher than the water surface. How high is the water in centimeters?
一个长方体水箱从里面量长是40厘米，宽30厘米，箱中水面高度10厘米，放进一个棱长20厘米的正方体后，铁块顶面仍高于水面．这时水面高多少厘米？
<gadget id="calculator">12_000 / 800</gadget>
<output>15</output>

<result>15</result>