There are 140 students in the playground. After the boys left (1/10), 50 girls came. At this time, the number of boys and girls is equal. How many girls were there in the playground?
操场上共有学生140人，男生走掉(1/10)后，女生来了50人，这时男、女生人数相等，操场上原来有女生多少人．
<gadget id="calculator">140 + 50</gadget>
<output>190</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 + (9/10)</gadget>
<output>19/10 = around 1.9</output>

<gadget id="calculator">190 / (19/10)</gadget>
<output>100</output>

<gadget id="calculator">140 - 100</gadget>
<output>40</output>

<result>40</result>