Transcript Lesson 2-Estimating With Percents

6-2 Estimating with Percents
Warm Up
Problem of the Day
Lesson Presentation
Lesson Quizzes
6-2 Estimating with Percents
Warm Up
Write each percent as a fraction and as a
decimal.
1. 75% 3, 0.75
4
2. 10% 1 , 0.1
10
3. 32% 8 , 0.32
25
4. 17% 17 , 0.17
100
6-2 Estimating with Percents
Problem of the Day
You are biking to the library. When you
are 75% of the way there, you realize
you forgot a book. So you turn around
1
and head back. When you are of the
3
way back you realize you don’t need the
book, so you turn around again and bike
3.2 miles back to the library. How far do
you live from the library?
6.4 miles
6-2 Estimating with Percents
Learn to estimate percents.
6-2 Estimating with Percents
The table shows common percents and their
fraction equivalents. You can use fractions to
estimate the percent of a number by choosing a
fraction that is close to a given percent.
Percent
10%
20%
25%
Fraction
1
10
1
5
1
4
1
33 3 %
50%
2
663 %
1
3
1
2
2
3
6-2 Estimating with Percents
Additional Example 1: Using Fractions to Estimate
Percents
Use a fraction to estimate 27% of 63.
Think: 27% is about 25% and
1
25% is equivalent to .
4
 1 · 60 Change 63 to a compatible
4
number.
 15
Multiply.
27% of 63 is about 15.
27% of 63  1 · 63
4
Remember!
Compatible numbers are close to the numbers in the problem
and help you use mental math to find a solution.
6-2 Estimating with Percents
Check It Out: Example 1
Use a fraction to estimate 48% of 91.
48% of 91  1 · 91
2
Think: 48% is about 50% and
1
50% is equivalent to .
2
 1 · 90
2
Change 91 to a compatible
number.
 45
Multiply.
48% of 91 is about 45.
6-2 Estimating with Percents
Additional Example 2: Consumer Math Application
Tara’s T’s is offering 2 T-shirts for $16, while
Good-T’s is running their buy one for $9.99,
get one for half price sale. Which store offers
the better deal?
First find the discount price for 2 t-shirts at Good T’s.
50% of $9.99 = 1 · $9.99 Think: 50% is equivalent to 1 .
2
2
Change $9.99 to a
 1 · $10
compatible number.
2
Multiply.
 $5
The second shirt cost approximately $5. Since $10
+ $5 = $15, the 2 T-shirts for $15 at Good-T’s is
the better deal.
6-2 Estimating with Percents
Check It Out: Example 2
Billy’s Office Supply Store is offering 25% off a
leather notebook, originally priced at $9.75. K’s
Office Supply Store offers the same notebook,
not on sale, at $7.00. Which store offers the
better deal?
First find the discount on the notebook at Billy’s Office Supply.
25% of $9.75 = 1 · $9.75
4
 1 · $10
4
 $2.50
Think: 25% is equivalent to 1 .
4
Change $9.75 to a compatible
number.
Multiply.
The discount is approximately $2.50. Since $10 - $2.50 =
$7.50, the notebook from K’s Office Supply Store is the
better deal.
6-2 Estimating with Percents
Another way to estimate percents is to find
1% or 10% of a number. You can do this
by moving the decimal point in the number.
1% of 45 = .45. 10% of 45 = 45.
.
To find 1% of a
number, move the
decimal point two
places to the left.
To find 10% of a
number, move the
decimal point one
place to the left.
6-2 Estimating with Percents
Additional Example 3A: Estimating with Simple
Percents
Use 1% or 10% to estimate the percent of
each number.
4% of 18
18 is about 20, so find 4% of 20.
1% of 20 =.20.
4% of 20 = 4 · 0.2 = 0.8 4% equals 4 · 1%.
4% of 18 is about 0.8.
6-2 Estimating with Percents
Additional Example 3B: Estimating with Simple
Percents
Use 1% or 10% to estimate the percent of
each number.
29% of 80
29% is about 30, so find 30% of 80.
10% of 80 = 80.
.
30% of 80 = 3 · 8.0 = 24.0 30% equals 3 · 10%.
29% of 80 is about 24.
6-2 Estimating with Percents
Check It Out: Example 3A
Use 1% or 10% to estimate the percent of
each number.
5% of 14
14 is about 15, so find 5% of 15.
1% of 15 =.15.
5% of 15 = 5 · 0.15 = 0.75 5% equals 5 · 1%.
5% of 14 is about 0.75.
6-2 Estimating with Percents
Check It Out: Example 3B
Use 1% or 10% to estimate the percent of
each number.
21% of 60
21% is about 20, so find 20% of 60.
10% of 60 = 60.
.
20% of 60 = 2 · 6.0 = 12.0 20% equals 2 · 10%.
21% of 60 is about 12.
6-2 Estimating with Percents
Additional Example 4: Consumer Math Application
Tim spent $58 on dinner for his family. About
how much money should he leave for a 15%
tip?
Since $58 is about $60, find 15% of $60.
15% = 10% + 5%
Think: 15% is 10% + 5%.
10% of $60 = $6
1
5% is 2 of 10% so divide
5% of $60 = $6 ÷ 2 = $3
$6 + $3 = $9
$6 by 2.
Add the 10% and 5%
estimates.
Tim should leave about $9 for a 15% tip.
6-2 Estimating with Percents
Check It Out: Example 4
Amanda spent $12 on a hair cut. About how
much money should she leave for a 15% tip?
Since $12 is about $10, find 15% of $10.
15% = 10% + 5%
Think: 15% is 10% + 5%.
10% of $10 = $1
1
5% is 2 of 10% so divide
5% of $10 = $1 ÷ 2 = $0.50
$1 + $0.50 = $1.50
$1 by 2.
Add the 10% and 5%
estimates.
Amanda should leave about $1.50 for a 15% tip.
6-2 Estimating with Percents
Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems
6-2 Estimating with Percents
Lesson Quiz
1. Use a fraction to estimate 48% of 72. 36
2. A café is offering 10% off the $4.99 lunch. If a
diner is offering the same lunch for $4.59, which
The café
is offering the better deal?
Use 1% or 10% to estimate the percent of each
number.
Possible answers:
3. 4% of 220 8.8
4. 19% of 75
15
5. Mr. and Mrs. Dargen spend $46.25 on a meal.
About how much should they leave for a 15% tip?
$7
6-2 Estimating with Percents
Lesson Quiz for Student Response Systems
1. Use a fraction to estimate 52% of 84.
A. 30
B. 40
C. 50
D. 60
6-2 Estimating with Percents
Lesson Quiz for Student Response Systems
2. During the annual sale, Brand A offers 20%
off on a $6.55 shirt. Which of the following
will make Brand B a better deal?
A. Brand B sells the same shirt for $4.89.
B. Brand B sells the same shirt for $5.59.
C. Brand B sells the same shirt for $5.89.
D. Brand B sells the same shirt for $6.29.
6-2 Estimating with Percents
Lesson Quiz for Student Response Systems
3. Use 1% or 10% to estimate 6% of 239.
A. 2.4
B. 14.4
C. 16.6
D. 24
6-2 Estimating with Percents
Lesson Quiz for Student Response Systems
4. Use 1% or 10% to estimate 18% of 88.
A. 8.8
B. 14
C. 18
D. 22
6-2 Estimating with Percents
Lesson Quiz for Student Response Systems
5. Patricia bought accessories worth $52.75
in an online store. About how much would
she spend for a 13% shipping charge?
A. $5
B. $7
C. $9
D. $13