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Subtracting decimals: 9.57-8.09

To find the least common denominator of two fractions, we can either list out the multiples of the two denominators until we find a common one, or use prime factorization. Once we've found the least common denominator, we can rewrite the fractions so they both have this denominator, and then add them together. Created by Sal Khan.

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Video transcript

Let's try to subtract 9.57 minus 8.09. So try to pause this video and figure this out first before we work through it together. All right. Well, let's just rewrite it. Let's rewrite it. And when I rewrite it, I like to line up the decimals. This one it's a little intuitive. We have 8.09. Just like that, and now we're ready to subtract. And we want to subtract 9 hundredths from 7 hundredths. Well, we don't have enough hundredths up here so let's move over here. Let's see if we can do some regrouping so we always have a higher number on top. So over here we want to subtract 0 tenths from 5 tenths so we have enough tenths over here. So let's regroup. So instead of 5 tenths, I'm going to have 4 tenths, and then I'm going to give that other tenth, which is the same thing as 10 hundredths over here, so this becomes 17 hundredths. 17 minus 9 is 8. 4 minus 0 is 4. And then I have 9 minus 8 is 1. So this is going to be 1.48.