What is the largest prime factor of 90?
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Correct!
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Correct answer to question 105 (Mathematics Knowledge): 5
Method
Breaking 90 down gives 2 x 3 x 3 x 5, so its prime factors are 2, 3, and 5, and the largest is 5. The choice 45 is a factor of 90 but is not prime.
Updated: November 2026
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