Xiaopang takes 10 yuan to the stationery store to buy fountain pens. He wants to buy 4 fountain pens, but he still needs 2 yuan and 40 cents. How much is each fountain pen?
小胖带10元钱去文具店买水笔，他要买4支水笔，还缺少2元4角，每支水笔多少元？
<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">2 + (2/5)</gadget>
<output>12/5 = around 2.4</output>

<gadget id="calculator">10 + (12/5)</gadget>
<output>62/5 = around 12.4</output>

<gadget id="calculator">(62/5) / 4</gadget>
<output>31/10 = around 3.1</output>

<result>31/10 = around 3.1</result>