Mineral water in a supermarket costs 5 yuan for 4 bottles when purchased, and 5 yuan for 3 bottles when sold. If you want to make a profit of 300 yuan, how many bottles of this mineral water need to be sold.
某超市的矿泉水，进货时4瓶5元，售出时3瓶5元，要想获利300元，需售出这样的矿泉水多少瓶．
<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(5/3) - (5/4)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">300 / (5/12)</gadget>
<output>720</output>

<result>720</result>