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Welcome to Brainfuse!
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In this lesson we'll work on addition with decimals and the trick to doing these problems is taking the
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time to set them up correctly. We're going to do a sample problem, it asks us to
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Find the sum of 8.756, 0.2935,
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And 9.6.
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Let's set that up and we need to
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Make sure to align
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the decimal points.
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Okay so,
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I know that I can get easily confused since the numbers are different lengths
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So what I can do
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Is add zeros as placeholders, they don't add any value to the
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decimals,
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but
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They allow you to make sure
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the digits in each
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decimal place are lined up correctly.
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So, before we start, we're going to also remember to add that decimal
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point to the sum, we make sure it is aligned with the addends
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So we start on the far right, there we have 5 + 2 zeros,
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6 + 3 is 9,
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9 + 5 is 14,
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I dropped the 4 and carry the one
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7 + 1 is 8, plus 2 is 10, plus 6 is 16. Drop the 6, carry the 1.
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8 + 1 is 9, plus 9 is 18
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Okay, so that is the sum of these decimals
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And
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You think that it would be much easier if you just use the calculator right, but actually a lot of mistakes can
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happen, because
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You usually cannot make sure that your decimal points are aligned when you're using
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the calculator.
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If you do get to use one in class, then you want to check your
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answer by estimating what it would actually be
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You can do that by just rounding the decimals. Let's say that I have this number
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On my calculator screen and I want to make and I want to make sure that it makes sense
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So I'm just going to round these two whole numbers.
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And make sure that this sum is in the ballpark of the sum I get when I round the numbers. So rounding them into whole numbers, 8.7,
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7 will make me round up to 9
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With 0.2,
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I'd stay at 0.
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9.6, the 6 is above 5 so we'd round
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And that gives us 19, which is close to 18.6 so I can tell that okay,
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My answer makes sense and I can go on with life and go onto the next problem. Thank you for watching this lesson.