No, the ratios 2:1 and 1:2 are not same

Example: Let A : B = 2 : 1

=> A/B = 2/1 = k(let)   where k is a constant

=> A/2 = B/1 = k

=> A= 2k and B = k

Again let A : B = 1 : 2

=> A/B = 1/2 = k(let)   where k is a constant

=> A/1 = B/2 = k

=> A= k and B = 2k

In both the cases, values of A and B are different.

So both ratios are different.