rounding decimals unit 3.2 pages 104-107. 1. 18.74, 18.7, 18.47 2. 9.06, 9.66, 9.6, 9.076 3.3.072...
TRANSCRIPT
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.