There are 50 parts in a batch, and it is known that the pass rate of this batch of parts is 90%, how many parts in this batch are unqualified.
一批零件有50个，已知这批零件的合格率为90%，则这批零件不合格的有多少个．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">50 * (9/10)</gadget>
<output>45</output>

<gadget id="calculator">50 - 45</gadget>
<output>5</output>

<result>5</result>