Video: Writing a Number in Appropriate Significant Figures

A can contains 375 mL of soda. How much is left after 308 mL is removed?


Video Transcript

A can contains 375 milliliters of soda. How much is left after 308 milliliters is removed?

This exercise involves combining two numbers and keeping track of the significant figures involved for our answer. We’re told that we start with 375 milliliters of soda in a can. We then remove 308 of those milliliters. And we want to know how much is leftover. What we’re doing is combining two numbers through subtraction, that each have three significant figures in them.

If we perform the subtraction directly, we get a result of 67 milliliters. But the question is, since each of the numbers we added together has three significant figures, does our answer need to have three as well? In other words, would we report 67.0 milliliters as our result?

We can recall the rule that when we’re adding or subtracting numbers, the way to keep track of significant figures, is to round our answer to the least number of decimal places involved. The two numbers we’re working with, both have zero decimal places. So, our final answer will as well. The amount of soda leftover is 67 milliliters.

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