SOLUTION: Which set of numbers is not closed under multiplication? odd integers, even integers, prime numbers, or rational numbers.

Question 257495: Which set of numbers is not closed under multiplication? odd integers, even integers, prime numbers, or rational numbers.
Answer by drk(1908) (Show Source): You can put this solution on YOUR website!
Primes are not closed under multiplication.
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Look at each separately:
odd integers: odd x odd = odd [closed]
even integers: even x even = even [closed]
prime numbers: prime x prime = composite [NOT closed]
rational numbers: fraction x fraction = fraction [closed]
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