In this number classification question, four four digit numbers are given. Three of them are not divisible by 5, while one of them is clearly divisible by 5 because of its last digit. Using basic divisibility rules, find out the odd number from the given alternatives.

Introduction / Context:
This question focuses on simple divisibility rules, especially divisibility by 5. You are given four four digit numbers: 3425, 4541, 5661 and 6783. In competitive exams, examiners often test whether you remember quick mental checks such as looking only at the last digit to decide whether a number is divisible by 5. Here, three numbers do not satisfy this rule, while one number clearly does. The goal is to identify the number that behaves differently under the divisibility by 5 test and mark it as the odd one out.

Given Data / Assumptions:

• Numbers: 3425, 4541, 5661 and 6783.
• We are interested in divisibility by 5.
• A number is divisible by 5 if and only if its last digit is 0 or 5.
• Exactly one number ends in 5, the others end in 1 or 3.
• No additional hidden pattern is assumed beyond this clear divisibility test.

Concept / Approach:
To decide whether a number is divisible by 5, you do not need long division. The standard rule says: if the last digit of a number is 0 or 5, then the number is divisible by 5; otherwise, it is not. Therefore, in a list of numbers, the simplest way to spot which ones are multiples of 5 is to look only at the units place. In an odd one out question, if only one option satisfies this rule, then that option is the odd one based on divisibility by 5.

Step-by-Step Solution:
Step 1: Examine 3425.The last digit is 5. Therefore, 3425 is divisible by 5.Step 2: Examine 4541.The last digit is 1, so 4541 is not divisible by 5.Step 3: Examine 5661.The last digit is 1, so 5661 is also not divisible by 5.Step 4: Examine 6783.The last digit is 3, so 6783 is not divisible by 5.Step 5: Compare all four numbers.Only 3425 passes the divisibility by 5 test, while the other three numbers do not. That makes 3425 the odd number in this group.

Verification / Alternative check:
You can quickly verify your conclusion by attempting to divide each number by 5 in your head. Dividing 3425 by 5 gives 685 exactly, which is an integer. On the other hand, dividing 4541, 5661 or 6783 by 5 yields non integer results ending in .2 or .4 etc. This confirms that only 3425 is a multiple of 5 and clearly supports the choice based on the divisibility rule without any ambiguity.

Why Other Options Are Wrong:
4541: Ends in 1, so it fails the divisibility by 5 rule and is not a multiple of 5 like 5661 and 6783.
5661: Ends in 1, therefore this number is also not divisible by 5.
6783: Ends in 3, so it is not divisible by 5 and behaves like 4541 and 5661 under this rule.

Common Pitfalls:
Some candidates spend time looking for complicated patterns involving sums or products of digits, or possible relationships between the thousands, hundreds, tens and units digits. While deeper patterns sometimes appear, in this case the examiner is simply checking whether you can apply the basic divisibility rule. Always test simple rules like divisibility by 2, 3, 5 or 9 when you see larger numbers; they often reveal the intended structure very quickly and save valuable exam time.

Final Answer:
The odd number is 3425, because it is the only number in the list that is divisible by 5, while 4541, 5661 and 6783 are not divisible by 5.