A mathematical thinking problem, 10 people in the class get it wrong, and 30 people get it right, what is the correct rate of this problem?
一道数学思考题，全班10人做错，30人做正确，这道题的正确率是多少．
<gadget id="calculator">30 + 10</gadget>
<output>40</output>

<gadget id="calculator">30 / 40</gadget>
<output>3/4 = around 0.75</output>

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

<gadget id="calculator">(3/4) * 1</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>