There are 50 students in a class of five years. In an exam, 90% of them scored more than 60 points. How many of them failed.
五年一班有50名学生，在一次考试中，得60分以上的有90%，有多少人不及格．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">50 * (1/10)</gadget>
<output>5</output>

<result>5</result>