Free Practice Question
PS · Problem Solving
705-805
Combinations
How many 4-digit even numbers are there with distinct digits?
Answer Choices
Correct answer marked belowA
2250
2296
Correct
C
2520
D
4499
E
4500
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Explanation
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Official Explanation
Official
We need to count 4-digit even numbers with distinct digits.
Case 1: The last digit is 0.
The number is of the form _ _ _ 0.
First digit (thousands place) cannot be 0, so choices = 9 digits (1-9).
Second digit: any of the remaining 8 digits (excluding the first digit and 0).
Third digit: any of the remaining 7 digits.
Last digit is fixed as 0.
Count = .
Case 2: The last digit is 2, 4, 6, or 8 (4 possibilities).
The number is of the form _ _ _ (even digit).…
Case 1: The last digit is 0.
The number is of the form _ _ _ 0.
First digit (thousands place) cannot be 0, so choices = 9 digits (1-9).
Second digit: any of the remaining 8 digits (excluding the first digit and 0).
Third digit: any of the remaining 7 digits.
Last digit is fixed as 0.
Count = .
Case 2: The last digit is 2, 4, 6, or 8 (4 possibilities).
The number is of the form _ _ _ (even digit).…
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What it tests
Whether you can count arrangements and selections correctly — permutations vs. combinations.
Common trap
Overcounting: treating a selection as ordered when order does not matter, or forgetting to divide by duplicates.
Details
Difficulty
705-805
Type
PS
Category