There are 18 people with excellent rope skipping results in Class 6 1, and the excellent rate is 45%. How many people are there in Class 1 Class 6?
六1班跳绳成绩优秀的有18人，优秀率是45%，六1班有多少人．
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">18 / (9/20)</gadget>
<output>40</output>

<result>40</result>