There are 42 students in the first class of the third grade, and 40 students in the second class. How many double desks are needed for the two classes?
三年级一班有42人，二班有40人，两个班共需要多少张双人课桌？
<gadget id="calculator">42 + 40</gadget>
<output>82</output>

<gadget id="calculator">82 / 2</gadget>
<output>41</output>

<result>41</result>