There are two cuboid tanks A and B without a cover. Among them, tank A contains some water, and tank B is empty. Measured from the inside, tank A is 40 cm long, 30 cm wide, 50 cm high, and 21 cm high on the water surface; tank B is 30 cm long, 20 cm wide, and 50 cm high. Now pour part of the water in tank A into tank B, so that the height of the water in the two tanks is the same. What is the height in centimeters in the two tanks now?
有甲、乙两个无盖的长方体水箱．其中，甲水箱里装有一些水，乙水箱空着．从里面量，甲水箱长40厘米，宽30厘米，高50厘米，水面高21厘米；乙水箱长30厘米，宽20厘米，高50厘米．现将甲水箱中的一部分水倒入乙水箱，使两个水箱里的水面高度相同，问现在两个水箱里的高度是多少厘米？
<gadget id="calculator">40 * 30</gadget>
<output>1_200</output>

<gadget id="calculator">30 * 20</gadget>
<output>600</output>

<gadget id="calculator">1_200 + 600</gadget>
<output>1_800</output>

<gadget id="calculator">21 / 1_800</gadget>
<output>7/600 = around 0.011667</output>

<gadget id="calculator">40 * 30 * (7/600)</gadget>
<output>14</output>

<result>14</result>