six. On Children's Day, the students went to visit the Science and Technology Museum. It is known that the number of students in the fifth grade is 30 times less than that in the fourth grade, 240 people in the fifth grade, and how many people in the fourth grade?
六．一儿童节，同学们去参观科技馆，已知五年级去的人数比四年级的3倍少30人，五年级去了240人，四年级去了多少人？
<gadget id="calculator">240 + 30</gadget>
<output>270</output>

<gadget id="calculator">270 / 3</gadget>
<output>90</output>

<result>90</result>