A discount store of a certain brand launched a year-end promotion. The original unit price of a product was 160 yuan. Now buy 3 and get 1 free. In this way, how much is the product cheaper per piece?
某品牌折扣店年终开展促销活动，原来某商品单价为160元，现在买3送1．这样算来，该商品每件便宜多少元？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">160 * (3/4)</gadget>
<output>120</output>

<gadget id="calculator">160 - 120</gadget>
<output>40</output>

<result>40</result>