Xiao Ming took some yuan to go shopping in the supermarket. He used (1/4) to buy books, (1/5) to buy snacks, and the rest to buy aircraft model materials. What is the total amount of money for aircraft model materials? What percentage?
小明带若干元钱去超市购物，他用其中的(1/4)买图书，用其中的(1/5)买零食，剩下的部分购买了航模材料，问购买航模材料的钱占总数的几分之几？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/4) - (1/5)</gadget>
<output>11/20 = around 0.55</output>

<result>11/20 = around 0.55</result>