When a shop buys 4 bottles of mineral water for 5 yuan, and when it sells 2 bottles for 5 yuan, how many bottles need to be sold in order to make a profit of 100 yuan?
商店矿泉水进货时5元钱4瓶，售出时5元钱2瓶，要获利100元，需售出多少瓶？
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

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

<gadget id="calculator">(5/2) - (5/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">100 / (5/4)</gadget>
<output>80</output>

<result>80</result>