Boss Zhang said: "I bought a batch of cloth shoes at a price of 2,640 yuan, and sold them at a price of 8 yuan per pair. Today, only one-tenth of the shoes are left. I have recovered all the shoes, and I have made a profit." 240 yuan". Q: How many pairs of shoes did he buy?
张老板说："我以2640元的价钱购进一批布鞋，又以每双8元的价格卖出，到今天只剩下十分之一了，已收回了全部鞋款，而且已获利240元"．问：他购进的鞋一共有多少双？
<gadget id="calculator">2_640 + 240</gadget>
<output>2_880</output>

<gadget id="calculator">2_880 / 0.72</gadget>
<output>4_000</output>

<result>4_000</result>