Question 1106657: How many two-digit even numbers can you form using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9?
A.repetition is allowed
B.no repetition
Found 2 solutions by Edwin McCravy, ikleyn:
Answer by Edwin McCravy(20060)   (Show Source):
You can put this solution on YOUR website!
If we could have 0 come first, and we didn't care
whether they were even or odd, there would be these 100:
00, 01, 02, 03, ..., 08, 09, 10, 11, ..., 98, 99
We take away these 10, which are really 1-digit numbers:
00, 01, 02, 03, ..., 08, 09
and that leaves these 90:
10, 11, ..., 98, 99
half of those 90 are even and the other half odd, and
since half of 90 is 45, we have these 45
10, 12, ..., 96, 98
So 45 is the answer to (a)
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Now if we take away these 4 with repetition:
22, 44, 66, 88
then we have only 41
So 41 is the answer to (b)
Edwin
Answer by ikleyn(52803)  (Show Source):
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