Dongdong’s house was 4 kilometers away from Liangliang’s house. When Dongdong walked 1,000 meters, he returned home to pick up things, and then went to Liangliang’s house to play. How many kilometers did Dongdong walk in total?
东东家到亮亮家共有4Km，东东走了1000米时，又返回家中取东西，然后到亮亮家玩，东东一共走了多少千米？
<gadget id="calculator">2 / 1_000</gadget>
<output>1/500 = around 0.002</output>

<gadget id="calculator">1_000 * (1/500)</gadget>
<output>2</output>

<gadget id="calculator">2 + 4</gadget>
<output>6</output>

<result>6</result>