The school organizes interest groups, with 40 participants in the sixth grade and 36 participants in the fifth grade. The number of participants in the sixth grade is twice that of the fourth grade. What is the correct formula to calculate the number of students in three grades
学校举办兴趣小组，六年级有40人参加，五年级有36人参加，六年级参加的人数是四年级的2倍．要计算三个年级多少人参加，正确的算式是多少
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">20 + 36 + 40</gadget>
<output>96</output>

<result>96</result>