Liu Jia, who is studying at Jilin University, received a sum of money from her mother. She originally planned to spend 28 yuan a day, so the money would be enough for 30 days. Because she pays attention to saving, she actually only spends 21 yuan a day. How many days more than the original plan did the money actually cost?
在吉林大学读书的刘佳接到妈妈汇来的一笔钱，她原计划每天花28元，这样这笔钱，就够花30天．由于她很注意节约，实际每天只花21元，这笔钱实际比原计划多用了多少天？
<gadget id="calculator">30 / 21</gadget>
<output>10/7 = around 1.428571</output>

<gadget id="calculator">28 * (10/7)</gadget>
<output>40</output>

<gadget id="calculator">40 - 30</gadget>
<output>10</output>

<result>10</result>