_easurement and Signicant Figures You stretch a measuring tape across a kiddie pool and measure its diameter to the nearest centimeter (let's SE 153 cm). You pull out your calculator and multiply it by pi (7:) to get its circumference, so you can build a fenc around it. The calculator says 480.6636761 cm. Do you really know the pool's circumference to parts-per-billion precision? Or is the calculator just showing ya all those digits because it doesn't know any better? Any chain is only as strong as its weakest link. When it comes to the product or quotient of two or more numbers, the result is only as is only as "good" as the most-poorlyknown of those inputs. What makes a number \"good"that is, "well" or "poorly" known? Ultimately, it comes down to the amount of detail that we can use to describe it. "Fifteen percent" is more precise than "about one-sixth," and 0.156 is mt precise than "fifteen percent." What tells us how "well" or \"poorly" we know this number? The answer is the number of significant figures. Significant figures are those digits that convey reliable information about a numerical quantity. The number significant figures indicates the precision with which a quantity is known. When it comes to scientific measurements, the number of significant figures equals the number of digits used express that measurement (until zeroes are involved, as we'll learn at the end of this lesson). Let's go back to our kiddie pool. You measured a diameter of 153 cm. How many significant figures does 153: have? |:| Suppose you measured 153.7 cm for the pool's diameter: How many digits would then be significant? |:|