There are 40 people in the class doing a math problem, and 10 get it wrong. What is the correct rate of this problem?
一道数学题全班有40人做，10个做错，这道题的正确率是多少．
<gadget id="calculator">40 - 10</gadget>
<output>30</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>