There are four classes, with 90 people in Class 1 and Class 3, and 150 people in Class 2, Class 3, and Class 4. Class 3 accounts for 20% of the total number of people in Class 4. How many people are there in Class 3?
有四个班，一班、三班共90人，二班、三班、四班共150人，三班占四个班人数的20%，三班有多少人？
<gadget id="calculator">90 + 150</gadget>
<output>240</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">240 / (6/5)</gadget>
<output>200</output>

<gadget id="calculator">200 * (1/5)</gadget>
<output>40</output>

<result>40</result>