The clothing store has a year-end sales promotion. Originally, each pair of pants was 160 yuan. Now buy 3 pairs and get 1 free. If you buy 3 pairs at a time, how much is each pair cheaper than before?
服装店年终搞促销活动，原来每条裤子160元，现在买3条送1条，一次买3条，每条比原来便宜多少钱？
<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>