In physical education class, the students are all skipping rope or kicking shuttlecock, 45% of the total number of people only kicking shuttlecock, and 80% of the number of people only skipping rope, so how many people in the class take part in both sports? How much?
体育课上，同学们都在跳绳或踢毽子，只踢毽子的占总人数的45%，只跳绳的人数是只踢毽子人数的80%，那么两种运动都参加的占全班人数的几分之几？
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(9/20) * (4/5)</gadget>
<output>9/25 = around 0.36</output>

<gadget id="calculator">(9/20) + (9/25)</gadget>
<output>81/100 = around 0.81</output>

<gadget id="calculator">1 - (81/100)</gadget>
<output>19/100 = around 0.19</output>

<result>19/100 = around 0.19</result>