Students from Guiyuan Primary School released 2008 pigeons in the "Welcome to the Olympics" event, among which 508 were released by students from lower grades, and the ratio of the number of pigeons released by middle-grade students to senior students was 9:16. How many more do senior students release than middle-grade students?
桂园小学同学在"迎奥运"活动中共放飞了2008只鸽子，其中低年级同学放飞的有508只，中年级同学与高年级同学放飞只数的比是9：16．高年级同学比中年级同学多放飞多少只？
<gadget id="calculator">2_008 - 508</gadget>
<output>1_500</output>

<gadget id="calculator">9 + 16</gadget>
<output>25</output>

<gadget id="calculator">16 / 25</gadget>
<output>16/25 = around 0.64</output>

<gadget id="calculator">1_500 * (16/25)</gadget>
<output>960</output>

<gadget id="calculator">9 / 25</gadget>
<output>9/25 = around 0.36</output>

<gadget id="calculator">1_500 * (9/25)</gadget>
<output>540</output>

<gadget id="calculator">960 - 540</gadget>
<output>420</output>

<result>420</result>