It takes 4.5 hours to process a batch of 20 machines. If you add 5 identical machines, how many hours can it be completed? (column equation calculation)
一批零件20台机器加工需要4.5小时完成，如果增加相同的机器5台，可以几小时完成？(列方程计算)
<gadget id="calculator">1 / 90</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">(1/90) * 20</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">(1/90) * 5</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(2/9) + (1/18)</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">1 / (5/18)</gadget>
<output>18/5 = around 3.6</output>

<result>18/5 = around 3.6</result>