This Power Point presentation answers the question, "How many decimal places do we need to carry this out to?" It explains the need for significant figures by pointing out the ridiculousness of digits in calculations that go way beyond the precision of the instruments that derived the data. The presentation illustrates what place holders are, and teaches students how to count the number of significant figures in data. It also helps students develop rules for determining the appropriate number of significant figures in a calculation. As always, there are free supporting materials for the lesson on my web site, www.evanschemistrycorner.com .