Transcript Estimating with Percents

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Punchline worksheet #92
Text p. 238, #12-42 evens
In your journal, answer the following
question. A basketball costs $14.99 at
Modell’s. Sports Authority is offering the
same basketball at 20% off the regular
price of $19.99. Estimate to determine
which store is offering the better deal?
Punchline worksheet 92
“What Were the Crash Dummy’s Last
Words?”
GIVE ME A BRAKE
“Why Did the Little Boy Wear a Sheet to Go
Trick-or-Treating?”
HE WAS DRESSED UP AS A MATTRESS
Objective
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SWBAT estimate percents
Section 6.2
“Estimating with Percents”
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You can use fractions or decimals to
estimate with percents.
Estimating Percents with Fractions
You can estimate the percent of a number by
substituting a fraction that is close to a given percent.
Percent
10%
Fraction
1
10
20%
25%
1
33 3 %
1
5
1
4
1
3
A basketball costs $14.99 at
Modell’s. Sports Authority is
offering the same basketball at
20% off the regular price of
$19.99. Estimate to determine
which store is offering the better
deal?
Find 20% of $19.99
50%
2
66 3 %
1
2
2
3
1
  20
5
 $4.00
Compatible numbers –
numbers that are close and help you
use mental math to find the solution
Finding Percent of a Number
means multiplication
Use a fraction and compatible numbers to estimate the
percent of each number.
Find 25% of 35.
25%
Find 34% of 63.
34%
1
4
1
 36
4
1
3
1 63

3 1
1 36 36 9
 


4 1
4 1
1 63 63 21
  

3 1
3
1
Find 8% of 261.
8%
1
10
1 260 260 26
1


 260  
10 1
10
1
10
Estimating Percents with Decimals
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%
Find
of any
number by moving the
decimal point 2 places to
the left.
Find 1% of 45
45.0 = 0.45
10%
Find
of any
number by moving the
decimal point 1 place to
the left.
Find 10% of 45
45.0 = 4.5
Use 1% or 10% to estimate the
percent of each number.
Find 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.
Find 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.
Real-Life 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.
Real-Life Application
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.
NJASK7 Prep
Homework
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Text p. 238, #12-42 evens