There is a bucket of water that weighs 100 kg, and when half of the water is used, the weight of the bucket is 60 kg. How many kilograms of water are there in the bucket?
有一桶水连桶重100千克，用去一半的水后，连桶重60千克．桶里原有多少千克水？
<gadget id="calculator">100 - 60</gadget>
<output>40</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<result>80</result>