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The number of integers greater than 2000 that can be formed with the digits 0, 1, 2, 3, 4, 5, using each digit at most once, is

A. 1240
B. 1280
C. 1320
D. 1380

User Tom Womack
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Final answer:

To find the number of integers greater than 2000 with the digits 0, 1, 2, 3, 4, 5 without repetition, we calculate permutations for both four-digit and five-digit numbers. There are 240 four-digit numbers and 120 five-digit numbers, totaling 360 possible integers.

Step-by-step explanation:

The question asks us to calculate the number of integers greater than 2000 that can be formed using the digits 0, 1, 2, 3, 4, 5 without repetition. To ensure the integers are greater than 2000, the first digit must be either 2, 3, 4, or 5. Once the first digit is chosen, there are 5 remaining digits for the second place, 4 for the third place, and 3 for the fourth place, considering that zero cannot be the first digit of the integer.

Therefore, we calculate the number of combinations as follows:

4 options for the first digit (since the number has to be greater than 2000)

5 options for the second digit

4 options for the third digit

3 options for the fourth digit

The total number of combinations is the product of these options: 4 × 5 × 4 × 3 = 240.

However, this accounts only for four-digit numbers. Since we can also form five-digit numbers with the provided digits, we need to consider that scenario as well. For five-digit numbers, all five non-zero digits can be used as the first digit, followed by permutations of the remaining four digits.

Therefore, we can form additional combinations as follows:

5 options for the first digit

4 options for the second digit (after choosing the first digit)

3 options for the third digit

2 options for the fourth digit

1 option for the fifth digit

The total number of five-digit combinations is the product of these options: 5 × 4 × 3 × 2 × 1 = 120.

Adding both four-digit and five-digit combinations gives us the total number of integers: 240 + 120 = 360.

User Bruno Eberhard
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