Master Wang processes a batch of parts. After 5 days of production, the ratio of the number of unmade parts to the total number of parts is 3:5. If 240 parts are processed again, the excess will be 20%. How many parts are there in this batch?
王师傅加工一批零件，做了5天以后，未做零件的个数与零件总个数的比是3：5，如果再加工240个零件就超额20%．这批零件有多少个？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(6/5) - (2/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">240 / (4/5)</gadget>
<output>300</output>

<result>300</result>