Talk:Architecture (Age of Empires II)/@comment-180.254.41.30-20170130152141/@comment-27198062-20170205114539

The bonus is just multiplicative and not additive. So it's not (HP)+(10%*HP+10%*HP), but (HP)*110%*110%, totalling 121% instead of 120% of the base HP (HP*1.1*1.1=HP*1.21).