Data Sufficiency (DS) | Re: What is the greatest common divisor of integers r and s ?

r =a × b
s =a × c
GCD (r, s) =a

2r =2 ×a × b
2s =2 ×a × c
GCD (2r, 2s) =2a

No matter r and s have or don't have the number 2 as one of its factors respectively, 2r and 2s always include the number 2 as one of their common divisor.
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