Xiaohong has to walk 1.8 kilometers from home to school. When she walked 0.4 kilometers, she found that she forgot her math books. She immediately returned home to get the math books. How many kilometers did Xiaohong walk to school?
小红从家到学校要走1.8千米，当她走了0.4千米的时候发现数学书忘记带了，立即按原路返回家拿数学书，小红走到学校一共要走多少千米？
<gadget id="calculator">0.4 * 2</gadget>
<output>0.8</output>

<gadget id="calculator">0.8 + 1.8</gadget>
<output>2.6</output>

<result>2.6</result>