Master and apprentice process a batch of parts. The apprentice processed 40 parts, 20% less than the master. How many parts did the master process?
师徒加工一批零件．徒弟加工了40个，比师傅少20%，师傅加工了多少个零件？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">40 / (4/5)</gadget>
<output>50</output>

<result>50</result>