A garment factory plans to produce a batch of garments in 20 days. Due to the production of 10 more pieces per day, the task was completed 4 days ahead of schedule. How many pieces of clothing are in this batch?
一个服装厂计划20天生产一批服装．由于每天多生产10件，结果提前4天完成任务，这批服装是多少件？
<gadget id="calculator">10 * 20</gadget>
<output>200</output>

<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">200 - 40</gadget>
<output>160</output>

<gadget id="calculator">4 - 20</gadget>
<output>-16</output>

<gadget id="calculator">20 + (-16)</gadget>
<output>4</output>

<gadget id="calculator">160 / 4</gadget>
<output>40</output>

<gadget id="calculator">40 * 20</gadget>
<output>800</output>

<result>800</result>