There are 27 people who go to the shopping mall to buy water to drink. When the shopping mall is running a promotion, three empty bottles can be exchanged for one bottle of water. Ask: 27 people, at least how many bottles of water should they buy so that everyone has a bottle of water to drink.
有27个人到商场去买水喝，遇到商场搞促销，三个空瓶子就可以换一瓶水，问：27个人，最少只买多少瓶水，使每个人都有一瓶水喝．
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">27 * (2/3)</gadget>
<output>18</output>

<result>18</result>