math problem, 40 people in the class get it right and 10 people get it wrong, what is the correct rate of the whole class on this problem?
一道数学题，全班同学中40人做对，10人做错，全班同学做这道题的正确率是多少．
<gadget id="calculator">40 + 10</gadget>
<output>50</output>

<gadget id="calculator">40 / 50</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">(4/5) * 1</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>