Some products in a supermarket are on sale. Each box of candy is 15 yuan. Buy 4 boxes and get 1 box free. Xiaomin bought 4 boxes. How much can each box be cheaper?
某超市部分商品搞促销活动，每盒糖果15元，买4盒送1盒，晓敏买了4盒，每盒能便宜多少钱？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 * (1/5)</gadget>
<output>3</output>

<result>3</result>