Jingang Elementary School held a class sports meeting, and each student only participated in one event. The fifth grade students participated in the track competition (2/5) of the whole grade, and the field competition accounted for the whole grade (9/20), and the rest participated in the group gymnastics performance. What percentage of the whole grade take part in group gymnastics performances?
金岗小学举行班运动会，每人只参加一项，五年级同学参加径赛的占全年级的(2/5)，参加田赛的占全年级的(9/20)，其余的参加团体操表演．参加团体操表演的占全年级的几分之几？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">9 / 20</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">1 - (2/5) - (9/20)</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>