Use the numbers on the three cards 2, 4, and 5 to form several different three-digit numbers. What is the average of all these three-digit numbers?
用2、4、5三张卡片上的数字组成若干个不同的三位数，所有这些三位数的平均数是多少．
<gadget id="calculator">245 + 254 + 425 + 452 + 542 + 524</gadget>
<output>2_442</output>

<gadget id="calculator">2_442 / 6</gadget>
<output>407</output>

<result>407</result>