The machine tool factory processes a batch of parts. The ratio of the number of processed parts to the total number is 1:4 in the first week, and 390 parts are processed in the second week. At this time, the ratio of the number of processed parts to the number of unprocessed parts is 3:4. , how many parts are there in total?
机床厂加工一批零件，第一周加工的个数与总个数的比是1：4，第二周又加工了390个，这时加工的和未加工的零件个数比是3：4，这批零件一共有多少个？
<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(3/7) - (1/4)</gadget>
<output>5/28 = around 0.178571</output>

<gadget id="calculator">390 / (5/28)</gadget>
<output>2_184</output>

<result>2_184</result>