A large harvester can harvest the wheat of a certain farm in 20 days, and a medium harvester can harvest the wheat of this farm in 40 days. The large and medium-sized harvesters harvested at the same time for 10 days. Due to a new task, the large-scale harvester was transferred to another place, and the rest was completed by the medium-sized harvester. How many days will it take for the medium-sized harvester?
一台大型收割机可用20天收割完某农场的小麦，一台中型收割机可用40天收割完这个农场的小麦．大、中型收割机同时收割了10天，因有新的任务，大型收割机调到他处，剩下的由中型收割机完成收割任务，中型收割机还需要多少天？
<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/40) + (1/20)</gadget>
<output>3/40 = around 0.075</output>

<gadget id="calculator">(3/40) * 10</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) / (1/40)</gadget>
<output>10</output>

<result>10</result>