How Many Numbers Greater Than 2000 Can Be Formed Using Digits 0, 1, 2, and 4?

How Many Numbers Greater Than 2000 Can Be Formed Using Digits 0, 1, 2, and 4?

In this article, we will explore how many numbers greater than 2000 can be formed using the digits 0, 1, 2, and 4, with the condition that each digit can only be used once. We will analyze this problem through both a brute force approach using the J programming language and a more analytical approach using combinatorial mathematics.

Brute Force Solution using J Programming Language

We begin by defining the problem in the J programming language. The J language provides powerful capabilities for combinatorial problems, which makes it well-suited for this task.

n.~ 4{0 1 2 4
12

The result of this computation indicates that 12 numbers greater than 2000 can be formed using the digits 0, 1, 2, and 4. The numbers are listed as follows:

2014 2041 2104 2140 2401 2410 4012 4021 4102 4120 4201 4210

Analysis of the Results

The brute force method provides us with 12 numbers, but to gain a deeper understanding, we will also explore the problem using combinatorics.

Using Combinatorics

To systematically determine the number of possible numbers, we'll break down the problem based on the number of digits in the number:

Five-Digit Numbers

Five-digit numbers cannot start with 0, so we have 4 options for the ten-thousands place (1, 2, 4). For each choice, the remaining four digits can be arranged in 4! (24) ways. Therefore, there are:

4 * 24 96 five-digit numbers

Four-Digit Numbers Greater than 3000

To form four-digit numbers greater than 3000, the thousands place must be either 4 or 5. This gives us 2 options for the thousands place for each option, the remaining three digits can be placed in 4P3 (24) ways. Our total count for four-digit numbers greater than 3000 is:

2 * 24 48 numbers

Adding these two counts together, we get:

Total numbers greater than 3000 96 (five-digit) 48 (four-digit) 144 numbers

Combining the Results

We can combine both the brute force and combinatorial methods to confirm our answer. From the brute force method, we identified 12 numbers greater than 2000. Now, using the combinatorial approach, we confirmed that there are an additional 132 numbers (144 - 12 132) that are greater than 2000. This breakdown reaffirms our total of 144 numbers.

Conclusion

In conclusion, 144 unique numbers greater than 2000 can be formed using the digits 0, 1, 2, and 4, with each digit used only once. This approach combines both a practical and theoretical understanding of the problem, verifying the result through multiple methods.