RoundingDecimals

Unit 3.2Pages 104-107

1. 18.74, 18.7, 18.47

2. 9.06, 9.66, 9.6, 9.076

3. 3.072

4. 6.158

18.47, 18.7, 18.74

9.06, 9.076, 9.6, 9.66

Three and seventy two thousandths

Six and one hundred fifty eight thousandths

Warm Up Problems Order the numbers from LEAST to GREATEST?

Write in words

Estimating Decimals.

Objective: Students will be able to estimate decimal sums, differences, products and quotients by clustering, using place value, grouping and using front/back end estimation.

A decimal helps us to see what numbers are WHOLE numbers, and what

numbers are PARTS OF THE WHOLE.

Wholes Parts of the Whole

Definitions

Clustering: Rounding numbers to the same value (amount).

Front-End Estimation: Use the whole numbers in the decimals to estimate values (amounts).

Let’s review some definitions that we should already know.

Sum

Difference

Product

Quotient

Addition

Subtraction

Multiplication

Division

We use decimal estimation in real word situations?

Can you think of any?

We will be solving equations with decimals using a few different

strategies:

PlaceValue

Clustering

FrontEnd

Comparable

Numbers

Estimate numbers with decimals by rounding to the indicated place value.

Look at the digit to the right of your place value.

If it is a 5 or greater round up one number.

If it is less that 5 round down by adding zero’s.

3.92 + 6.48

ONES

3.92 + 6.483.92 + 6.484.00 + 6.00

4 + 6 = 10

PlaceValue

Estimate numbers with decimals by rounding to the indicated place value.

Look at the digit to the right of your place value.

If it is a 5 or greater round up one number.

If it is less that 5 round down by adding zero’s.

2.746 – 0.866tenths

2.7 – .9 = about 1.8

PlaceValue

#2.

Estimate numbers with decimals by rounding to the indicated place value.

Look at the digit to the right of your place value.

If it is a 5 or greater round up one number.

If it is less that 5 round down by adding zero’s.

6.735 + 4.9528ones

7.0 + 5.0 = about 12

PlaceValue

#3.

We will be solving equations with decimals using a few different

strategies:

PlaceValue

Clustering

FrontEnd

Comparable

Numbers

When numbers are close to the same amount, you can use

clustering: changing all amounts to same value.

Someone who weighs about 90 pounds can burn the following calories:

Activity Calories Estimation

Bicycling 198.45

Playing Ice Hockey 210.60

Rowing 224

Water Skiing 194.4

200.00200.00200.00200.00

Clustering

Ella will run about _____ total miles .

Ella runs three days a week. She ran 3.62 miles on Monday, 3.8 miles on Wednesday, and 4.3 miles on Friday. About how any miles did she

run on last week?

Days of the Week Miles Estimation

Monday 3.62

Wednesday 3.8

Friday 4.3

4.004.004.00

12

Clustering

#1.

Estimate Each Product or Quotient

Compatible numbers areclose to the

numbers that are in the problem,

and can be helpful when you

are solving estimations

using MENTAL MATH.

CompatibleNumbers

26.76 x 2.93

25 x 3

about75

26.76 x 2.93

Estimate Each Product or Quotient

Compatible numbers areclose to the

numbers that are in the problem,

and can be helpful when you

are solving estimations

using MENTAL MATH.

CompatibleNumbers

42.64 16.51

40 / 20

about2

42.64 16.51

Estimate Each Product or Quotient

Compatible numbers areclose to the

numbers that are in the

problem, and can be helpful when you are

solving estimations

using MENTAL MATH.

CompatibleNumbers

38.92 4.06

__ /__

About _______

#6

Estimate Each Product or Quotient

Compatible numbers areclose to the

numbers that are in the

problem, and can be helpful when you are

solving estimations

using MENTAL MATH.

CompatibleNumbers

14.75 x 7.89

__ /__

About _______

#7

When using the Front End Estimation

Strategy we look at the

WHOLE number, in front of the decimal and estimate for that number

before adding or subtracting the amounts.

9.99 22.89+ 8.30

9 22+ 8 39

Front and Back End

Estimation

When using the Back End Estimation

Strategy we look at the

WHOLE number, in back of the decimal and estimate for that number

before adding or subtracting the amounts.

9.99 22.89+ 8.30

1.00 1.00+ .502.50

Front and Back End

Estimation

We can now take the two

amounts, add them together and find the

RANGEFor the sum.

9.99 22.89+ 8.30

39 + 2.50

Front and Back End

Estimation

The range is 39 to 41.50

Find the range for each sum.

7.8 31.39+ 6.95

Front and Back End

Estimation

The range is about 46 to 48.40

8.0031.00 7.0046.00

1.00 .40 1.00 2.40

#9.

Find the range for each sum.

14.27 5.4+21.86

Front and Back End

Estimation

The range is about 41 to 42.70

14.00 5.0022.0041.00

.30 .40 1.00 1.70

#10.

3.2 HomeworkPage 106-107 Due: Thursday

12-26Mrs. Saucedo’s class

12-19

3.0744 + 1.352

7.305 – 4.1268

4.5

914

3

Round to the tenth place value Round to the nearest whole place

Estimate each product or quotient

6.75 x 1.82

Estimate each product or quotient

10.5 3.42