Sixth grade students participated in the activity, half of them climbed mountains with 4 people, the remaining half of them went boating with 10 people, and the remaining 40 people watched animals. How many people in the sixth grade participated in the activity?
六年级同学参加活动，其中的一半又4人爬山，余下的人数的一半又10人划船，还剩下40人观看动物．六年级共有多少人参加活动．
<gadget id="calculator">40 + 10</gadget>
<output>50</output>

<gadget id="calculator">50 * 2</gadget>
<output>100</output>

<gadget id="calculator">100 + 4</gadget>
<output>104</output>

<gadget id="calculator">104 * 2</gadget>
<output>208</output>

<result>208</result>