(a) What is the GCF of 33 and 42 using prime factors?
(b) What is the GCF of 72 and 30 by dividing by prime factors?
(c) What is the GCF of 27, 76, and 34 by making a list of factors?
Answer (2)
( a ) 33∣ 3 11∣11 . 1∣ − − − − − − − − − 42∣2 21∣ 3 . 7∣7 . 1∣ − − − − − − − − − − GCF ( 33 ; 42 ) = 3
( b ) 2 ∣72 30 .3 ∣36 15 ... ∣12 5 GCF ( 72 ; 30 ) = 2 × 3 = 6
( c ) f a c t ors o f 27 : 1 ; 3 ; 9 ; 27 f a c t ors o f 76 : 1 ; 2 ; 4 ; 19 ; 38 ; 76 f a c t ors o f 34 : 1 ; 2 ; 17 ; 34 GCF ( 27 ; 76 ; 34 ) = 1 T h e n u mb ers 27 ; 76 an d 34 a re co p r im e n u mb ers .
The GCF of 33 and 42 is 3. The GCF of 72 and 30 is 6. The GCF of 27, 76, and 34 is 1, indicating they are coprime.
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