Master Wang processes a batch of parts. The ratio of the number of qualified parts to the number of unqualified parts is 4:1. What is the pass rate of this batch of parts?
王师傅加工一批零件，合格零件数与不合格零件数的比是4：1，这批零件合格率是多少？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(4/5) * 1</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>