There is a piece of bronze, which is made of three metals: copper, tin and zinc. Among them, copper accounts for (3/5) of the total weight, tin accounts for (1/4) of the total weight, and what percentage of zinc accounts for the total weight?
有一块青铜，是由铜、锡和锌三种金属熔合而成的．其中铜占总重量的(3/5)，锡占总重量的(1/4)，锌占总重量的几分之几？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(3/5) + (1/4)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">1 - (17/20)</gadget>
<output>3/20 = around 0.15</output>

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