There are many people on the playground, some of them are standing and some are sitting. If 25% of the standing people sit down and 25% of the sitting people stand up, then the standing people account for 70% of the people on the playground. %, what percentage of the number of people on the playground are those who were originally standing?
操场上有很多人，一部分站着，另一部分坐着，如果站着的人有25%坐下，而坐着的人中有25%站起来，那么站着的人就占操场上人数的70%，求原来站着的人占操场上人数的百分之几？
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(7/10) - (1/4)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(3/4) - (7/10)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(9/20) / (1/20)</gadget>
<output>9</output>

<gadget id="calculator">1 + 9</gadget>
<output>10</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>