A factory plans to process a batch of parts. After processing (3/5) of the plan, another 840 parts are processed. At this time, the total number of parts processed has increased by 10% compared with the plan. How many parts were originally planned to be processed?
某厂计划加工一批零件，加工完计划的(3/5)后，又加工了840个，这时加工的总数比计划增加了10%，原计划加工多少个？
<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">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(2/5) + (1/10)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">840 / (1/2)</gadget>
<output>1_680</output>

<result>1_680</result>