Since my other post was ignored, I'm reposting a greatly summarized, simplified version. Can someone teach me the basics of working with significant numbers? Here's the 2 example problems I'm working on. Display the answer to the correct number of significant digits. 1. 142.47 + 30.2 2. 342 x 12 To read the problems I'm having and my attempts at the solutions, see this thread: https://www.physicsforums.com/showthread.php?t=135362 A quick, non-specific, crash course in layman's terms would be most helpful. Thanks.