The school organizes students to visit the science and technology exhibition. There are 250 senior students, which is 70 people less than twice the number of middle grade students. How many middle grade students went there?
学校组织同学们参观科技展览，高年级去了250人，比中年级去的人数的2倍少70人，中年级去了多少学生？
<gadget id="calculator">250 + 70</gadget>
<output>320</output>

<gadget id="calculator">320 / 2</gadget>
<output>160</output>

<result>160</result>