The school checks the hygiene of 20 classes, 18 classes are "excellent", 2 classes are "good", what is the excellent rate
学校检查20个班的卫生，18个班为"优秀"，2个班为"良好"，优秀率是多少
<gadget id="calculator">18 / 20</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(9/10) * 1</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>