9-1: Relating Fractions,
Decimals, and Percents
IWBAT convert a percent to a fraction or decimal and convert a fraction or
decimal to a percent.
Percent – A special ratio that compares a
number with 100 Percent means “per hundred”
Vocabulary
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
Examples
1) 2) 3)
Percent to Decimal and Fraction
Percent to Decimal
Remove the % sign Move the decimal
left twice
Percent to Fraction
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
9-2: Estimating Percent
IWBAT estimate percents of numbers between 0% and 100% using multiples
of 10% or fractions
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
Estimating Using Rounding
Examples
1) Estimate 28% of 71
2) Estimate 9% of $19.99
3) Estimate 82% of 202 4) Estimate 89% of 6
Memorize the following common percent to
fraction conversions:
Round the whole number to the nearest 10s Choose the corresponding fraction Multiply
Estimating Using Fractions
10% 20% 25% 33% or
34%
50% 66% or
67%
75% 90%
Examples
1) 75% of 200 2) 39% of 600 3) 21% of 400
4) 26% of 19 5) 92% of 48
9-3: Finding a Percent of a
Number
IWBAT use a proportion to set up percent problems and solve using cross
products.
Think of problems as asking, “What is . . . ?”
Percent Proportion Formula
9-4: Is an Estimate Enough?
IWBAT determine whether an estimate is a sufficient solution or whether an
exact amount is needed.
9-5: Mental Math: Finding a Percent
of a Number
IWBAT use mental math to calculate percents of numbers
Use the same rules as estimating percent
9-6: Solving Percent Problems Using Equations
IWBAT write and solve percent equations.
Break up the problem and substitute into
proper place in proportion formula
Use the Percent Proportion Formula
Write a proportion and solve.
What number is 25% of 62?
1) Break into sections. What number is25%Of 62
2) Substitute into formula
25100
=𝑛62
3) Simplify, if possible
4) Cross-Multiply
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?
9-7: Write an Equation
IWBAT writ and solve one-step linear equation involving percent
9-8: Finding Sales Tax
IWBAT find sales tax and total cost.
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
Vocabulary
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
0.95485
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
$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.
9-9: Computing Discount
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
3.9975
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
$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: 33
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?
9-10: Using the Interest Formula
IWBAT use the simple interest formula to calculate interest and find the total
amount earned or charged.
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)
Vocabulary
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?
2) Rewrite the interest formula
I = prt
1) Identify each variable I = ?p = $200r = 5.5% = 0.055t = 1
3) Substitute. Solve the equation to find interest.
I = prtI = 200(0.055)(1)I = $11
4) Add the interest to the principal
$200 + 11 = $211
Examples
1) Principal: $6,000 Rate: 5% Time: 5 months
Find the interest and the total with interest.
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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