Odd One Out — From the pairs 23–29, 19–25, 13–17, 3–5, select the pair that does not consist of two primes.

Introduction / Context:
Prime recognition is a staple in classification problems. Here, three pairs contain only primes; the remaining pair includes a composite number.

Given Data / Assumptions:

• Pote ntial primes: 3, 5, 13, 17, 19, 23, 29.
• 25 is 5 * 5 and therefore composite.

Concept / Approach:
Check each element for primality using small divisibility tests (2, 3, 5, 7) appropriate to the magnitude.

Step-by-Step Solution:
23–29: both prime.13–17: both prime.3–5: both prime.19–25: 25 is composite (5^2), so this pair breaks the pattern.

Verification / Alternative check:
Square bounds: 25 is a perfect square; perfect squares greater than 1 are never prime. This confirms the outlier quickly.

Why Other Options Are Wrong:

• 23–29: prime pair.
• 13–17: prime pair.
• 3–5: prime pair.

Common Pitfalls:
Assuming any odd number is prime; 25 is an instructive counterexample.

Final Answer:
19-25