Trigonometry Workbook For Dummies
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When you want to add large numbers, you can stack them on top of each other so that the ones digits line up in a column, the tens digits line up in another column, and so on. You then add column by column, starting from the ones column on the right. Not surprisingly, this method is called column addition. Here’s how you add 55 + 31 + 12. First add the ones column:

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Next, move to the tens column:

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This problem shows you that 55 + 31 + 12 = 98.

Sometimes when you’re adding a column, the sum is a two-digit number. In that case, you need to write down the ones digit of that number and carry the tens digit over to the next column to the left — that is, write this digit above the column so you can add it with the rest of the numbers in that column. For example, suppose you want to add 376 + 49 + 18. In the ones column, 6 + 9 + 8 = 23, so write down the 3 and carry the 2 over to the top of the tens column:

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Now continue by adding the tens column. In this column, 2 + 7 + 4 + 1 = 14, so write down the 4 and carry the 1 over to the top of the hundreds column:

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Continue adding in the hundreds column:

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This problem shows you that 376 + 49 + 18 = 443.

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Mary Jane Sterling taught algebra, business calculus, geometry, and finite mathematics at Bradley University in Peoria, Illinois, for more than 30 years. She is the author of several For Dummies books, including Algebra Workbook For Dummies, Algebra II For Dummies, and Algebra II Workbook For Dummies.

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