> speed = 1/70= (100% + %faster)(1/80) > %faster = 80/70 - 100% = 14.3% Just want to add: % faster should only be use for small percentage Bruce Dawson recommend around 20% https://randomascii.wordpress.com/2018/02/04/what-we-talk-about-when-we-talk-about-performance/ We don't say 100% faster, we say twice as fast -- the number is bigger, good for marketing -- using speed ratio is unambiguous (faster if ratio > 1) -- work well even if code run slower, say 0.96X -- trivial to calculate speed vs oldest version = 1.143 * 0.96 = 1.097X