4 Digit Positive Integers
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- Newbie | Next Rank: 10 Posts
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Here is another method
since you want only even numbers, the last digit can be 0,2,4,6,8. Number of ways of choosing one digit out of these is 5C1 = 5
1st digit can be 1..9 (excluding 0)..so number of ways = 9C1=9
2nd digit can be 0..9..so number of ways =10C1=10
3rd digit can be 0..9..so number of ways =10C1=10
So total = 9*10*10*5 = 4500
since you want only even numbers, the last digit can be 0,2,4,6,8. Number of ways of choosing one digit out of these is 5C1 = 5
1st digit can be 1..9 (excluding 0)..so number of ways = 9C1=9
2nd digit can be 0..9..so number of ways =10C1=10
3rd digit can be 0..9..so number of ways =10C1=10
So total = 9*10*10*5 = 4500