Some water has already been put in the drinking bucket, and water is added to the drinking bucket later, and the water added each time is twice the water in the previous bucket. After adding 3 times, the weight of water in the drinking bucket is exactly 54 kg. So how many kilograms of water is in the original drinking bucket?
饮水桶里原来已经放了一些水，以后再往饮水桶里加水，每次加的水都是前一次桶里的水的2倍．加了3次后饮水桶里的水重正好是54千克．那么原来饮水桶里有水多少千克．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 3</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">18 + 9</gadget>
<output>27</output>

<gadget id="calculator">54 / 27</gadget>
<output>2</output>

<result>2</result>