What is the median of data 2, 4, 5, 7.
数据2，4，5，7，的中位数是多少．
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>