Jingtou Township needs to renovate a section of (4/5) kilometers long river course. Repair (1/2) kilometers in the first ten days, repair 250 meters in the middle ten days, and repair the rest in the last ten days. How many kilometers will be repaired in the second half of the year?
井头乡要整修一段长(4/5)千米的河道．上旬整修(1/2)千米，中旬整修250米，剩下的下旬修整．下旬还要修整多少千米？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(4/5) - (1/2) - (1/4)</gadget>
<output>1/20 = around 0.05</output>

<result>1/20 = around 0.05</result>