Math For Elementary Teachers

Part 3iii: Greatest Common Factor


You may have noticed a couple of errors in the previous clip. One was small, the other, not so much!

Error #1: When writing out the prime factorizations of 72 and 80, I mentioned that “we can list all divisors of 72 from the prime factorization”. This is almost true, but not quite, as 1 is a divisor of 72 but is not a prime factor of 72. I should have said “we can list all divisors of 72 (except 1) from the prime factorization”.

Error #2: You all probably caught this one; when computing GCF(72,180) I forgot a common factor of 3; so GCF(72,180) is not 12, as I falsely stated, but instead is 2 \cdot 2 \cdot 3 \cdot 3 = 36.

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