Mathematics
Which of the following is a prime number?
69
87
91
97
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Answer
69 = 3 × 23, so 69 is not prime.
87 = 3 × 29, so 87 is not prime.
91 = 7 × 13, so 91 is not prime.
97: As 9 × 9 = 81 < 97 and 10 × 10 = 100 > 97, primes ≤ 9 are 2, 3, 5, 7. None of these divide 97. So 97 is prime.
Hence, option 4 is the correct option.
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