Chapter 2: Applications of Decimals

Section 2-1 Comparing and Rounding Decimals

• Rounding Decimals is similar to rounding whole numbers.

Example 1: Round 1.73628 to the nearest hundredth.

• Step one: locate the hundredth place.

• Step two: look at the digit to the right of the hundredths place.

• Step three: Is that # 5 or larger if so round up, if not the number stays the same.

• Write the new number.

• 1.74

More examples: Round 13.422 to the nearest tenth

• Step 1: Locate the tenth place

• Step2: look at the digit to the right of the tenths place.

• Step three: Is that # 5 or larger if so round up, if not the number stays the same.

• Write the new number.

• 13._

Get your marker and marker board, or paper and pencil.

• Working with the person beside you make up two problems and do the problems together.

Any questions?

• Work on your rounding assignment for 5 minutes quietly on your own.

Comparing Decimals

• Selected Information from Baseball Cards of Three Players (Topps 1993)

• Name Deer Dunston Rookie• At bats (AB) 393 73 26 • Hits (H) 97 23 5 • Doubles 20 3 1 • Triples 1 1 0 • Home runs 32 0 1 • Slugging % .547 .384 .346 • Batting Ave.247 .315 .192

How do we know which number is bigger 19.8,19.0, or 19.3?

• First compare the whole numbers (in this example the whole # is the same)

• Next compare the tenth place unit, and find which number is greater.

• The tenths are 8,0,3.

• Which is bigger?

• So _____ is the biggest.

Another example: Put these 3 #’s in order from least to greatest

7.58,7.59,7.54

• Hint: Look at whole number first

• Then go to the tenth place

• Then examine the hundredth place

• Correct order:____________________

Make up 1 set of decimal numbers and have the person next to you put them in order

from least to greatest.

How do we compare numbers?

• You can use a number line

• You can make a model

• You can use <, > symbols

Number Line

• Order 0.5,0.8, and 0.25 on a number line.

• _________________________________

0 1

Number Line

• Order 0.5,0.8, and 0.25 on a number line.

• _________________________________

0 0.25 0.5 0.8 1

Comparing using a model Draw a model of 0.58

Compare decimal numbers using <, > and = symbols

• < means less than

• > means greater than

• Compare 0.23 _____ 0.230

• Compare 4.79 _____ 4.8

• Compare 1.92 _____ 1.09

Practice

• Turn to the person next to you and compare numbers.

• You make up one number, your partner make up one number.

• Write them down comparing them using symbols.

Vocabulary word for this lesson

•   Equivalent decimals- numbers that name the same amount.

• Example: 0.4 and 0.40 are equivalent decimals. They name the same amount.

Review

• In this lesson you learned how to

• Round numbers

• Compare numbers to find least to greatest

• Compared numbers using…. Number line, models and symbols.

• Vocabulary word: Equivalent decimal

Assignment:

Rounding worksheet Due TodayAnd

Page 52-53 Problems 1-33 Due Monday