Xiao Ming bought 4 pens for 10 yuan, and got back 0.4 yuan. How much is each pen?
小明用10元买了4支钢笔，找回0.4元，每支钢笔多少元？
<gadget id="calculator">10 - 0.4</gadget>
<output>9.6</output>

<gadget id="calculator">9.6 / 4</gadget>
<output>2.4</output>

<result>2.4</result>