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To get the Greates Common Factor (GCF) of 170 and 820 we need to factor each value first and then we choose all the copies of factors and multiply them:
|170: ||2|| ||5||17|| |
|820: ||2||2||5|| ||41|
|GCF: ||2|| ||5|| || |
The Greates Common Factor (GCF) is: 2 x 5 = 10