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!
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