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Arithmetic (all content)

Course: Arithmetic (all content)>Unit 6

Lesson 7: Subtracting decimals

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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• So slightly off-topic...

I quit marijuana recently, and as I do these exercises and get further into Khan Academy, I keep wondering if people can do these exercises easily in their head. Give me a pen and paper and these problems are like nothing, because I understand them conceptually, but in my head I can barely keep track of the answers generated at each step.

Just curious if I'm the only one that needs a pen and paper for this simple stuff.
• Some people can do these kinds of things in their heads, but don’t beat yourself up if you can’t. It gets easier with practice and as you find your own shortcuts. :)
• I now how to do it but I can't do it sideways I now it doesn't mater if it is sideways or not
• Do it the way that makes it easier for you...but sometime in your life you will have to learn it sideways
• Here's a question, what's 95.23 minus 56.54? This may be easy to know so here it is! You take away the two to make it into one, and the three becomes 13 so 13 minus 4 is 9. You take away one number from five to four and then the one becomes into 11, and, 11 minus 5 is 6. You take away one number from nine to eight and the 4 becomes into 14, so 14 minus 6 equals 8. This is the last and most simple but not least, 8 minus 5 and it's 3! So, the answer was 38.69, and there it is!
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• my mom is making me do this
• so when you line up all the numbers will you subtract left to right or the other way around??
• Like any regular subtraction problem, you will subtract right to left.
• Great video and now I really now how to subtract decimals. Thank you?
• We never got are gifts for khan for hitting one hundred.