There are 3 classes in the third grade with an average of 40 students in each class, among which there are 39 students in the first class, 40 students in the second class, how many students are there in the third class.
三年级3个班平均每班有学生40人，其中一班有39人，二班有40人，三班有多少人．
<gadget id="calculator">40 * 3</gadget>
<output>120</output>

<gadget id="calculator">120 - 39 - 40</gadget>
<output>41</output>

<result>41</result>