The little sloppy had to walk 0.9 kilometers from home to school in the morning. After walking 100 meters, he found that he did not bring his math homework book, so he went home to get it. In this way, how many kilometers did he walk to school more than usual.
小马虎早上从家到学校上学，要走0.9千米，他走了100米后发现没有带数学作业本，又回家去取．这样他比平时上学多走了多少千米．
<gadget id="calculator">100 / 1_000</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 2</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>