Transcript powerpoint to review estimation of 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
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
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
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