[問題]天山04-22

[feebs79]

How many 4-digit positive integers are there in which all 4 digits are even?

A)625
B)600
C)500
D)400
E)256

Answer:D

我算法是C(4 ,1)*C(5 , 1)*C(5 , 1)*C(5 , 1)=4x5x5x5=500

請問為什麼是400勒?

Thank you!

[kwtluck]

答案是C,你的解答可能有誤~~

[feebs79]

撲...sorry...我看錯了....浪費版面

thanks