Can someone please explain me what is correct formula i excel.....I
need to markup or increase A1 for 30%

A1=16101.35
=A1*1.3 and that is 20931.75 (B1)
when I go to check =1-(A1/B1) i get 23%

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A1=16101.35
=A1/0.7 and that is 23001.93 (B1)
when I go to check =1-(A1/B1) i get 30%

So what is correct?