Uncle Wang processes a batch of parts. (2/5) of this batch of parts has already been processed, and only half is left after processing 40 more parts. How many parts are there in this batch?
王叔叔加工一批零件，已经加工了这批零件的(2/5)，再加工40个就只剩下一半，这批零件一共有多少个？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">40 / (1/10)</gadget>
<output>400</output>

<result>400</result>