In this three digit number permutation question, select the number that does not consist of the same three digits as the others: 358, 853, 538 and 240.

Introduction / Context:
Three digit odd one out questions often depend on permutations of the same set of digits. In such problems, three of the numbers are rearrangements of one another, while a fourth number uses completely different digits. You must identify the number that does not share the same digit set as the others, which tests both digit recognition and simple pattern spotting.

Given Data / Assumptions:

• The numbers given are 358, 853, 538 and 240.
• We examine the digits used in each number: hundreds, tens and units.
• The aim is to check which numbers are permutations of the same three digits.

Concept / Approach:
The approach is to break each number into its component digits and compare the sets. If three numbers are made from the same digits (for example 3, 5 and 8) in different orders, those three belong together. The number that uses a different set of digits becomes the odd one out. This does not require any complex calculation, just careful observation.

Step-by-Step Solution:
Step 1: For 358, the digits are 3, 5 and 8. Step 2: For 853, the digits are 8, 5 and 3, which is simply a different order of the same digits 3, 5 and 8. Step 3: For 538, the digits are 5, 3 and 8, again the same digits 3, 5 and 8 arranged differently. Step 4: For 240, the digits are 2, 4 and 0, which are not the same as 3, 5 and 8. Step 5: Thus 358, 853 and 538 are permutations of the same three digits 3, 5 and 8, whereas 240 has a different set of digits. Therefore 240 is the odd one out.

Verification / Alternative check:
We can write each number as a sorted digit set: 358 gives {3,5,8}, 853 gives {3,5,8}, 538 also gives {3,5,8}, and 240 gives {0,2,4}. The first three sets are identical, while the fourth is clearly different. Because the question is about number identity and not about value magnitude, the digit composition is the intended pattern. This confirms that 240 does not match the others.

Why Other Options Are Wrong:
358 is wrong as the odd one out because it shares the same digits as 853 and 538. 853 is wrong as the odd one out because it is simply a reorder of 358. 538 is wrong as the odd one out because it uses the same digits as 358 and 853 in another order.

Common Pitfalls:
A common mistake is to compare the numerical size of the numbers instead of their composition. Another is to overlook the digit zero in 240 and treat it as if it might be a rearrangement of the others. Carefully listing the digits avoids such confusion. Remember that in permutation based questions, the actual value is less important than which digits appear in the number.

Final Answer:
The only number that is not a permutation of the digits 3, 5 and 8, and thus the odd one out, is 240.