Transcript Estimation

Quick Review
Round to the place value of the underlined digit:
1. 3, 528
Answers:
2. 131,295
1. 3,500
3. 229,000
4. 995
2. 130,000
3. 200,000
4. 1,000
Using Estimation
Strategies
Section 1-1 (pages 5-9)
Estimate or Exact?
Suppose you are writing a news article. Your notes
contain some data that may be estimates. For each
situation, decide whether you have an estimate or an
exact value. Explain your decision.
a) The population of Florida is 16,000,000. Estimate
b) Florida has 25 representatives in the U.S. House of
Representatives. Exact Value
Other examples??
Things to Remember…

Estimate a number before you calculate it

Use the symbol
which means
“approximately equal to”
Estimating a Sum or
Difference

At the zoo, you see a Colombian black spider
monkey. The length of its body is 58.31 cm. The
Length of its tail is 78.96 cm. To the nearest tenth of
a centimeter, estimate the total length of the
monkey’s body and tail.
58.31 + 78.96
58.3 + 79.0
137.3 cm
Round to nearest tenth
Add
Estimating a Product

A rectangular kitchen is 8.5 ft long and 5.75 ft wide.
Use rounding to estimate the area of the kitchen in
square feet.
8.5
9
5.75
6
9*6 =
Round each factor to the nearest
whole number
54 ft2
Multiply
Extra Practice
Estimate. Round to the nearest whole number
before you add or subtract
1) 10.13 + 1.46
2) 14.17 - 10.92
3) 11.53 + 7.23
4) 9.35 - 0.81
11
3
19
8
Extra Practice
Estimate. Round to the nearest whole number
before you multiply.
1) 4.9 x 12.2
2) 6.07 x 3.29
3) 7.65 x 5.33
4) 25.123 x 4.79
60
18
40
125
Estimating by Front-End
Estimation

Useful for finding sums or differences.

Two Steps:
1) Add (Subtract) the front numbers
2) Estimate the sum of the lesser
numbers and adjust the estimate
Estimating by Front-End
Estimation

Suppose you went food shopping with your parents
this weekend and bought Lucky Charms for $3.21,
a frozen pizza for $4.79, Pepsi for $1.99, and a
pack of gum for $1.15. Estimate the total cost of
your purchases.
Step 1: Add
the front-end
digits
$3.21
$4.79
$1.99
Step 2: Estimate the total amount of
cents to the nearest dollar.
$3.21
$4.79
$1.99
+$1.15
+$1.15
$9
About $1
About $1
$2
The total cost is about $11.
Extra Practice

A group of runners run a relay race in which each
runner decides how long they run for. Their
distances were 3.9 miles, 2.1 miles, 1.7 miles, 1.2
miles, and 3.3 miles. Estimate the total distance of
the race.
Step 1: Add
the front-end
digits
3.9
2.1
1.7
1.2
+ 3.3
10
Step 2: Estimate the total amount of
tenths of a mile to the nearest mile.
3.9
2.1
About 1
1.7
1.2
About 1
+ 3.3
2
The total distance is about 12 miles.
Extra Practice
Use Front-End Estimation to estimate each sum.
1) 5.43 + 2.67
2) 8.09 + 11.24
3) 7.18 + 5.89
4) 3.62 + 2.31
8
19
13
6
What is a compatible
number?
Numbers that are easy to compute
mentally. You can use compatible
numbers to estimate.
 Change the numbers of the problem
to make the calculation easier.
 Useful for finding quotients.

Using Compatible Numbers

It took 75.75 pounds of shredded cheese to make
the world’s largest burrito. Use compatible
numbers to estimate how many 10 pound boxes of
shredded cheese the cooks needed.
75.75
Set up the Quotient
10
80
10
Choose compatible numbers
such as 10 and 80.
Extra Practice
Use compatible numbers to estimate each
quotient.
1) 76.5 ÷ 8.8
2) 19.45 ÷ 4.92
3) 103.6 ÷ 9.72
4) 32.2 ÷ 7.56
9
4
10
4