Section 3.2 Notes

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Transcript Section 3.2 Notes

Chapter 3
Decimals
Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc.
3.2
Comparing, Ordering,
and Rounding
Decimals
Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc.
Comparing Decimals
Comparing Two Numbers in Decimal Notation
1.
2.
Start at the left and compare corresponding digits. If the
digits are the same, move one place to the right.
When two digits are different, the large number is the one
with the larger digit.
The numbers in the tenths place are both 3.
The numbers in the hundredths place are different.
1.345
1.353
Since 4 < 5, we know that 1.345 < 1.353.
Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc.
Ordering Decimals
Example:
Place the following four decimals in order from
smallest to largest.
786.848
786.8 00
786.48 0
Add zeros to make the
comparison easier.
786.484
Rearrange with the smallest first.
786.48, 786.484, 786.8,
786.848
Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc.
Rounding Decimals
Rounding Decimals
1.
2.
3.
Find the decimal place (units, tenths, hundredths, and so
on) for which rounding is required.
If the first digit to the right of the given place value is
less than 5, drop it and all digits to the right of it.
If the first digit to the right of the given place value is 5
or greater, increase the number in the given place value
by one. Drop all digits to the right of this place.
346.74 8
Round the 4 up to 5.
346.74 2
hundredths place
Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc.
Do not round the 4 up.
hundredths place
Rounding Decimals
Example:
1. Round 198.438 to the nearest tenth.
198.438
198.4
2. Round 45.29502 to the nearest hundredth.
45.29502
45.30 = 45.3
Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc.