I guess the original question assumed that nitrogen would make up 89%, oxygen would be 10% and the rest of the gases would be 1%. The answer might be very different if the percentages were not as above.
Consider
79% nitrogen, 10% oxygen, 10% carbon dioxide and 1% other gases
Or
79% nitrogen, 10% oxygen, 10% chlorine and 1% other gases
Or
79% nitrogen, 10% oxygen, 10% helium and 1% other gases
Or
49% nitrogen, 10% oxygen, 40% carbon dioxide and 1% other gases
Recollect that the current atmosphere is about
79% nitrogen, 20% oxygen and 1% other gases
Correction
78% nitrogen, 21% oxygen and 1% other gases
The question should have been more precise. Ok so I am nit picking.