Holt CA Course 1 6-3 Estimating with Percents NS1.4 Calculate given percentages of quantities and...
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Transcript of Holt CA Course 1 6-3 Estimating with Percents NS1.4 Calculate given percentages of quantities and...
Holt CA Course 1
6-3 Estimating with Percents
NS1.4 Calculate given percentages of quantities and solve problems involving discounts at sales, interest earned, and tips.Also covered: NS2.1
California Standards
Holt CA Course 1
6-3 Estimating with Percents
The table shows common percents and their fraction equivalents. You can estimate a percent of a number by substituting a fraction that is close to a given percent.
Fraction
Percent 10% 20% 25% 50%33 %13 66 %
23
15
14
13
12
23
110
Holt CA Course 1
6-3 Estimating with Percents
Use a fraction to estimate 27% of 63.
Additional Example 1: Using Fractions to Estimate Percents
27% of 63 14
63
14
60
1527% of 63 is about 15.
Compatible numbers are close to the numbers in the problem and help you use mental math to find a solution.
Remember!
Think: 27% is about 25% and
25% is equivalent to .14
Change 63 to a compatible number.
Multiply.
Holt CA Course 1
6-3 Estimating with Percents
Use a fraction to estimate 48% of 91.
Check It Out! Example 1
48% of 91 12
91
12
90
45
48% of 91 is about 45.
Think: 48% is about 50% and
50% is equivalent to .12
Change 91 to a compatible number.
Multiply.
Holt CA Course 1
6-3 Estimating with Percents
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 50% off sale. Which store offers the better deal?
Additional Example 2: Consumer Math Application
First find the discount price for 2 t-shirts at Good T’s.
50% of $9.99 =12 $9.99
12
$10
$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.
Think: 50% is equivalent to .12
Change $9.99 to a compatible number.
Multiply.
Holt CA Course 1
6-3 Estimating with PercentsCheck It Out! Example 2
First find the discount on the notebook at Billy’s Office Supply.
25% of $9.75 = 14
$9.75
14
$10
$2.50
The discount is approximately $2.50. Since $10 – $2.50 = $7.50, the notebook from K’s Office Supply Store is the better deal.
Think: 25% is equivalent to .14
Change $9.75 to a compatiblenumber.
Multiply.
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?
Holt CA Course 1
6-3 Estimating with Percents
Another way to estimate percents is to find1% or 10% of a number. You can do thisby moving the decimal point in the number.
1% of 45 = 10% of 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.
. .0 45. 45.
Holt CA Course 1
6-3 Estimating with Percents
Use 1% or 10% to estimate the percent of each number.
Additional Example 3: Estimating with Simple Percents
A. 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% of 18 is about 0.8.
4% equals 4 · 1%.
.
Holt CA Course 1
6-3 Estimating with Percents
Use 1% or 10% to estimate the percent of each number.
Additional Example 3: Estimating with Simple Percents
B. 29% of 80
29% is about 30, so find 30% of 80.
10% of 80 = 80.
30% of 80 = 3 8.0 = 24.0
29% of 80 is about 24.
30% equals 3 · 10%.
.
Holt CA Course 1
6-3 Estimating with Percents
Use 1% or 10% to estimate the percent of each number.
Check It Out! Example 3
A. 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% of 14 is about 0.75.
5% equals 5 · 1%.
.
Holt CA Course 1
6-3 Estimating with Percents
Use 1% or 10% to estimate the percent of each number.
Check It Out! Example 3
B. 21% of 60
21% is about 20, so find 20% of 60.
10% of 60 = 60.
20% of 60 = 2 6.0 = 12.0
21% of 60 is about 12.
20% equals 2 · 10%.
.
Holt CA Course 1
6-3 Estimating with Percents
Tim spent $58 on dinner for his family. About how much money should he leave for a 15% tip?
Additional Example 4: Consumer Math Application
Since $58 is about $60, find 15% of $60.
15% = 10% + 5%
10% of $60 = $6
5% of $60 = $6 ÷ 2 = $3
$6 + $3 = $9
Tim should leave about $9 for a 15% tip.
Think: 15% is 10% + 5%.
5% is of 10% so divide $6 by 2.
12
Add the 10% and 5% estimates.
Holt CA Course 1
6-3 Estimating with Percents
Amanda spent $12 on a hair cut. About how much money should she leave for a 15% tip?
Check It Out! Example 4
Since $12 is about $10, find 15% of $10.
15% = 10% + 5%
10% of $10 = $1
5% of $10 = $1 ÷ 2 = $0.50
$1 + $0.50 = $1.50
Amanda should leave about $1.50 for a 15% tip.
Think: 15% is 10% + 5%.
5% is of 10% so divide $1 by 2.
12
Add the 10% and 5% estimates.