How many four digit natural numbers not exceeding the number 4321 can be formed using the digits1,2,3,4, if repetition is allowed?

Explanation

To solve the problem of how many four-digit natural numbers not exceeding 4321 can be formed using the digits 1, 2, 3, and 4 with repetition allowed, we will break it down into cases based on the thousands place.

### Step 1: Identify the cases based on the first digit (thousands place)

1. **Case 1**: The first digit (thousands place) is less than 4 (i.e., 1, 2, or 3).
- If the first digit is 1, 2, or 3, we can choose any of the 4 digits (1, 2, 3, 4) for the remaining three places (hundreds, tens, and units).
- Total combinations for this case:
- Choices for thousands place: 3 (1, 2, or 3)
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