Water is produced by the reaction of hydrogen and oxygen at a mass ratio of 1:8. How many kilograms of oxygen are needed to produce 6.3 kilograms of water?
水是由氢气和氧气按1：8的质量反应生成的，如果要生产6.3千克水，需要多少千克氧气？
<gadget id="calculator">1 + 8</gadget>
<output>9</output>

<gadget id="calculator">8 / 9</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">6.3 * (8/9)</gadget>
<output>5.6</output>

<result>5.6</result>