OpenStax College Physics, Chapter 1, Problem 4 (Problems & Exercises)

This is College Physics Answers with Shaun Dychko. We are going to express the 100 yard length of a football field in meters and we multiply by 3 feet for every yard to get rid of the yards units leaving us with feet and we want to do that because the conversion factor of the question tells us that there is 1 meter for every 3.281 feet and I write it this way so that the feet are on the bottom and they will cancel with these feet on the top here leaving us with meters behind. And our answer is 91.4 meters and the question is, how many significant figures should it have? Strictly speaking, when you have the number 100 written like this, this has only one significant figure however because we know this is the length of a football field, that detail is important because football fields are well standardized and in order to have fair gameplay, one should expect quite a precise measurement of a 100 yards for all the different football fields that the teams can play on. And so we can assume that this actually has three significant figures and so that's why 91.4 meters is the correct way to express this answer.