A math problem, 40 people in the class get it right and 10 people get it wrong, what is the error rate of this problem?
一道数学题，全班有40人做对，10人做错，这道题的错误率是多少．
<gadget id="calculator">40 + 10</gadget>
<output>50</output>

<gadget id="calculator">10 / 50</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">(1/5) * 1</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>