Qingshan Township needs to renovate a section of (4/5) kilometers long river course. Repair (1/2) kilometers in the first ten days, repair (1/4) kilometers 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?
青山乡要整修一段长(4/5)千米的河道．上旬整修(1/2)千米，中旬整修(1/4)千米，剩下的下旬整修．下旬还要整修多少千米？
<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>