A shopping mall launched a promotional activity "1 yuan for 2.5 yuan shopping coupon". A product is priced at 640 yuan, what is the promotional price?
某商场打出促销活动"1元钱换2.5元购物券"．某商品定价640元，问促销价是多少元．
<gadget id="calculator">640 / 2.5</gadget>
<output>256</output>

<result>256</result>