text: How do you find the GCF of 20, 21 and 25?
  
  Jan 9, 2017
  
  1
  
  Explanation:
  
  factors:
  
  $20 : \left\{1 , 2 , 4 , 5 , 10 , 20\right\}$
  
  $21 : \left\{1 , 3 , 7 , 21\right\}$
  
  $25 : \left[1 , 5 , 25\right]$
  
  $G C F = 1$