factory produces a batch of parts, and 84 of them are unqualified after inspection. At least how many parts must be qualified to ensure that the pass rate reaches 98%.
某工厂生产一批零件，经检验已有84个不合格，至少要有多少个合格，才能确保合格率达到98%．
<gadget id="calculator">98 / 100</gadget>
<output>49/50 = around 0.98</output>

<gadget id="calculator">1 - (49/50)</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">84 / (1/50)</gadget>
<output>4_200</output>

<gadget id="calculator">4_200 - 84</gadget>
<output>4_116</output>

<result>4_116</result>