Hope Primary School has 840 students. According to the survey, the ratio of parents who pick up and those who do not pick up is 2:5. How many students are not picked up by their parents?
希望小学有840名学生，据调查，家长接送和不接送的比是2：5．家长不接送的学生有多少名？
<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">840 * (5/7)</gadget>
<output>600</output>

<result>600</result>