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Select the option that does NOT belong to the same category as the others: 17, 27, 45, 81
17
27
45
81
17
Always check for prime numbers first in classification sets; if one number is prime and others are composite, that is the clear outlier.
Always check for prime numbers first in classification sets; if one number is prime and others are composite, that is the clear outlier.
Prime vs Composite Analysis
Identify the nature of each number: 17 is a prime number (only divisible by 1 and 17). 27, 45, and 81 are composite numbers.
Verification of Composites
27 = 3 * 9, 45 = 5 * 9, 81 = 9 * 9. All are divisible by multiple factors including 3 and 9, confirming they are composite.
B: 27 is a composite number (3³), C: 45 is a composite number (5 * 9), D: 81 is a composite number (9²).
A is correct because 17 is the only prime number in the set, while 27, 45, and 81 are all composite numbers.
If all numbers are odd, don't look for even/odd patterns; check for primality, perfect squares, or divisibility by a common factor.
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