The former term of the ratio is reduced by 3 times, and the latter term is enlarged by 3 times. At this time, the ratio is the original ratio.
比的前项缩小3倍，后项扩大3倍，这时比值是原来比值的多少．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

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

<result>1/9 = around 0.111111</result>