There are 30 students in Class 1, and the passing rate of a test is 90%. How many people fail?
六1班有学生30人，一次测验的及格率为90%，有多少人不及格．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">30 * (9/10)</gadget>
<output>27</output>

<gadget id="calculator">30 - 27</gadget>
<output>3</output>

<result>3</result>