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Question:
From the digits 0; first; 2; 3 ;4; How many different 4-digit odd numbers can 5 form?
Reference explanation:
Correct Answer:
Call the number you want to look up in the form abcd with (a, b, c, d) ∈ A = {0, 1, 2, 3, 4, 5}.
Since abcd is odd ⇒ d = {1, 3, 5} ⇒ d has 3 choices.
Then, a has 4 choices (other than 0 and d).
b has 4 choices and c has 3 choices.
So there are all 3.4.4.3 = 144 numbers to find.
Choose the answer C
ADSENSE
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