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Question
Explain why 3 × 5 × 7 + 7 is a composite number.
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Solution
We have, 3 × 5 × 7 + 7 = 7[3 × 5 + 1],
Which is not a prime number because it has a factor 7,
i.e. it has more than two factors.
Hence, it is a composite number.
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