Although I'd never watch it on my own, I know my wife is a fan of watching The Biggest Loser, so I joined her for an episode last night. They take the difference of those two numbers, and find the percentage of weight lost. They then rank everyone by percentage of weight lost, and the lowest two are eligible for elimination. 3.55 rounds up to 4 pounds, but what if we calculated those numbers for 3.55 pounds lost? Here's the math you need to know:If you're going to report a %-of-weight-lost to X significant digits, you need to measure the amount of weight lost to X significant digits.