Water is formed by the reaction of hydrogen and oxygen at a mass ratio of 1:8. If 7.2 kg of water is to be produced, how many kilograms of oxygen are needed?
水是由氢气和氧气按1：8的质量反应生成的，如果要生成7.2千克的水，需要氧气多少千克？
<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">7.2 * (8/9)</gadget>
<output>6.4</output>

<result>6.4</result>