Chapter 9x

Report
IWBAT convert a percent to a fraction or
decimal and convert a fraction or decimal to a
percent.
Vocabulary

 Percent – A special ratio that compares a number
with 100
 Percent means “per hundred”
Fraction to Decimal and
Percent

Fraction to Decimal
 Divide the numerator
by the denominator
 Put the whole number
in front of decimal, if
needed
Fraction to Percent
 Convert the fraction to
a decimal
 Move the decimal to
the right twice
 Add the % sign
3
1) 1 4
Examples

2)
3
5
3)
3
10
Percent to Decimal and
Fraction

Percent to Decimal
Percent to Fraction
 Remove the % sign
 Move the decimal left
twice
 Remove % sign
 Put number over 100
 Simplify
Examples

1) 15%
2) 2.75
3) 120%
Decimal to Fraction and
Percent

Decimal to Fraction
 Look at the place value
of the fraction
 Place decimal over
corresponding place
value
 Simplify
 Put whole number in
front if there is one
Decimal to Percent
 Move decimal right
twice
 Add the % sign
Examples

1) 3.15
2) 0.095
3) 0.65
IWBAT estimate percents of numbers
between 0% and 100% using multiples of 10%
or fractions
Estimating Using
Rounding

 Round the percent to the nearest 10%
 Round the number to the nearest 10s
 If the number is less than 10, do not round it
 Change the percent to a decimal
 Multiply
Examples

1) Estimate 28% of 71
2) Estimate 9% of $19.99
3) Estimate 82% of 202
4) Estimate 89% of 6
Estimating Using
Fractions

 Memorize the following common percent to fraction
conversions:
10%
20%
25%
1
10
1
5
1
4
33% or
34%
1
3
50%
1
2
66% or
67%
2
3
75%
90%
3
4
9
10
 Round the whole number to the nearest 10s
 Choose the corresponding fraction
 Multiply
Examples

1) 75% of 200
4) 26% of 19
2) 39% of 600
5) 92% of 48
3) 21% of 400
IWBAT use a proportion to set up percent
problems and solve using cross products.
Percent Proportion
Formula


%
100
=
()
ℎ ()
 Think of problems as asking, “What is . . . ?”
IWBAT determine whether an estimate is a
sufficient solution or whether an exact
amount is needed.
IWBAT use mental math to calculate percents
of numbers

 Use the same rules as estimating percent
IWBAT write and solve percent equations.
Use the Percent
Proportion Formula


%
100
=
 ()
ℎ ()
 Break up the problem and substitute into proper
place in proportion formula
Write a proportion and
solve.

What number is 25% of 62?
1) Break into sections.
2) Substitute into formula
3) Simplify, if possible
4) Cross-Multiply
What number is
25%
Of 62
25

=
100 62
Examples

1) 15 is what percent of 75?
2) What number is 40% of 88?
3) What percent of 90 is 27?
4) What is 120% of 360?
5) 16 is what percent of 40?
6) The 6th grade class is having a book sale. Their order included 300
novels. So far, 180 novels have been sold. What percent of the novels
have been sold?
IWBAT writ and solve one-step linear
equation involving percent
IWBAT find sales tax and total cost.
Vocabulary

 Tip – A percentage of the total of your bill that you
give for a service
 Tax – A percentage of the total of your bill that you
pay to the government
Finding Sales Tax and
Total Cost

You buy a soccer ball priced at $14.69. If the
rate of the sales tax is 6.5%, what is the total cost
of the ball?
1) Convert the percent to a decimal
6.5% = 0.065
2) Multiply the decimal by the
price. This is the sales tax.
14.69 ∙ 0.065
3) Round UP to the nearest cent
0.95485 ≈ 0.96
4) Add to the price to find the total
cost
$14.69 + 0.96
0.95485
$15.65
Examples

Find the sales tax and the total cost. Round the sales tax up to the
nearest cent.
1) Cost: $19
Rate of sales tax: 8%
2) Cost: $412
Rate of sales tax: 6%
3) Cost: $62.50
Rate of sales tax: 5.5%
4) A basketball costs $30. The rate of sales tax was 5%. Find the total cost of the
basketball.
IWBAT find discount and sales price.
Finding the Discount
and the Sale Price

The Nature Shop had a 25% sale on kaleidoscopes. Michael bought one
originally priced at $15.99. How much did he pay on sale?
1) Convert the percent to a decimal
25% = 0.25
2) Multiply the decimal by the
original cost. This is the discount.
15.99 ∙ 0.25
3) Round the discount DOWN to the
nearest cent.
3.9975 ≈ 3.99
4) Subtract the discount from the
original price to find the sale price.
$15.99 – 3.99
3.9975
$12.00
Examples

1) Regular price: $200
Rate of discount: 10%
2) Regular price: $56
Rate of discount: 25%
3) Regular price: $66
Rate of discount: 333 %
1
4) Tommy bought two kaleidoscopes on sale for 20% off. If each
kaleidoscope cost $29 before the sale, what did Tommy pay for both
on sale?
IWBAT use the simple interest formula to
calculate interest and find the total amount
earned or charged.
Vocabulary

 Interest – the amount of money paid for the use of
money
 Investments, loans, savings
 Interest Formula: I = prt
 I is interest
 p is principal (original amount deposited or
borrowed)
 r is the rate of interest (the percent earned or charged)
 t is the time the money is in the account or is borrowed
(measured in years)
Find the interest and
total with interest

You put $200 in a savings account earning 5.5% simple interest per year. What is
the total you will have in your account after one year?
1) Identify each variable
I=?
p = $200
r = 5.5% = 0.055
t=1
2) Rewrite the interest formula
I = prt
3) Substitute. Solve the
equation to find interest.
I = prt
I = 200(0.055)(1)
I = $11
4) Add the interest to the
principal
$200 + 11 = $211
Examples

Find the interest and the total with interest.
1) Principal: $6,000
Rate: 5%
Time: 5 months
2) Principal: $4,500
Rate: 18%
Time: 6 months
3) Principal: $500
Rate: 7.5%
Time: 1 year
4) You want to borrow $500,000 for 6 months at 12% interest.
How much money will you owe the bank?

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