Hydrogen and oxygen are synthesized into water according to the weight ratio of 1:8, how many kg of hydrogen are contained in 81 kg of water.
氢、氧按1：8的重量比合成水，81kg的水中，含氢多少kg．
<gadget id="calculator">1 + 8</gadget>
<output>9</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">81 * (1/9)</gadget>
<output>9</output>

<result>9</result>