Stellar Shoes Factory plans to make 3,200 pairs of sports shoes, with an average of 320 pairs per day in the first 5 days. In order to deliver ahead of schedule, the rest must be finished within 4 days. How many pairs per day on average?
恒星鞋厂计划做3200双运动鞋，前5天平均每天做320双，为了提前交货，剩下的要在4天内做完，平均每天要做多少双？
<gadget id="calculator">320 * 5</gadget>
<output>1_600</output>

<gadget id="calculator">3_200 - 1_600</gadget>
<output>1_600</output>

<gadget id="calculator">1_600 / 4</gadget>
<output>400</output>

<result>400</result>