Last Saturday, Spencer walked all over town running errands. First, he walked 0.3 of a mile from his house to the library and 0.1 of a mile from the library to the post office. Then he walked 0.4 of a mile from the post office back home. How many miles did Spencer walk in all?
<gadget id="calculator">0.3 + 0.1 + 0.4</gadget>
<output>0.8</output>

<result>0.8</result>