The garment factory held a year-end sales promotion. It used to be 160 yuan per pair of trousers, but now you buy three and get one free. If you buy three pairs of trousers at a time, how much is each pair of trousers cheaper than before?
服装厂年终搞促销活动，原来每条裤子160元，现在买三送一，一次买3条裤子，现在每条裤子比原来便宜多少钱？
<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>