A and B are two cylindrical containers with a bottom area ratio of 5:3. The depth of water in container A is 9 cm, and the depth of water in container B is 5 cm. Now fill the two containers with the same amount of water until the water depths are equal. How deep is the water in centimeters?
甲乙两个圆柱形容器，底面积比为5：3，甲容器内水深9厘米，乙容器内水深5厘米，现在这两个容器里注入同样多的水，直到水深相等为止．这时水深多少厘米？
<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">6 + 9</gadget>
<output>15</output>

<result>15</result>