The attendance rate of the sixth grade is 90%, and 4 people ask for leave. How many people are there in the sixth grade?
六年级的出勤率为90%，有4人请假，六年级有多少人．
<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">4 / (1/10)</gadget>
<output>40</output>

<result>40</result>