There are three classes A, B, and C. Class A has 50 people, Class B is from Class A (9/10), and Class C is from Class B (8/9). How many people are there in Class C?
甲、乙、丙三个班，甲班有50人，乙班是甲班的(9/10)，丙班是乙班的(8/9)．丙班有多少人？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">8 / 9</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">50 * (9/10) * (8/9)</gadget>
<output>40</output>

<result>40</result>