The price of milk in the store is 1.5 yuan per box. If there is a special sale in the store, buy 4 get 1 free, and you need to buy 30 boxes of milk, at least how much yuan you need to bring.
商店里牛奶每盒1.5元．如果商店里搞特卖活动，买4送1，要买30盒牛奶，至少要带多少元．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">30 / 5</gadget>
<output>6</output>

<gadget id="calculator">6 * 4 * 1.5</gadget>
<output>36</output>

<result>36</result>