There are 840 students in Guangming Primary School, among which third grade students account for (4/21) and sixth grade students account for (5/21). How many more sixth graders are there than third graders?
光明小学有学生840人，其中三年级学生占(4/21)，六年级学生占(5/21)．六年级学生比三年级多几人？
<gadget id="calculator">5 / 21</gadget>
<output>5/21 = around 0.238095</output>

<gadget id="calculator">840 * (5/21)</gadget>
<output>200</output>

<gadget id="calculator">4 / 21</gadget>
<output>4/21 = around 0.190476</output>

<gadget id="calculator">840 * (4/21)</gadget>
<output>160</output>

<gadget id="calculator">200 - 160</gadget>
<output>40</output>

<result>40</result>