Trigonometry Workbook For Dummies
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Rounding decimals works almost exactly the same as rounding numbers. You will usually need to round a decimal either to a whole number or to one or two decimal places.

To round a decimal to a whole number, focus on the ones digit and the tenths digit. Round the decimal either up or down to the nearest whole number, dropping the decimal point:


When the tenths digit is 5 (or greater), round the decimal up:


If the decimal has other decimal digits, just drop them:


Occasionally, a small change to the ones digits affects the other digits. (This may remind you of when the odometer in your car rolls a bunch of 9s over to 0s):


The same basic idea applies to rounding a decimal to any number of places. For example, to round a decimal to one decimal place, focus on the first and second decimal places (that is, the tenths and hundredths places):


To round a decimal to two decimal places, focus on the second and third decimal places (that is, the hundredths and thousandths places):


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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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