5 Minute Check
Complete on the back of your homework.
1. Best Buy is having a 30% off sale. You want to buy an
ipod that is marked $160. How much are you going to pay
before taxes?
2. If the tax rate was 6%, how much would the ipod cost
total?
3. Your bill at a restaurant is $25.60. You want to leave a
15% tip. How much money do you need for the entire bill?
5 Minute Check
Complete on the back of your homework.
1. Best Buy is having a 30% off sale. You want to buy an
ipod that is marked $160. How much are you going to
pay before taxes?
.30 x $160 = $48
This is the discount
$160 – $48 = $112
This is discounted price
Or you could have determined if the discount is 30%, then
you are paying 70%.
.7 x $160 = $112
5 Minute Check
Complete on the back of your homework.
2. If the tax rate was 6%, how much would the ipod cost
total?
5 Minute Check
Complete on the back of your homework.
2. If the tax rate was 6%, how much would the ipod cost
total?
.06 x $112 = $6.72
$112 + $6.72 = $118.72
Or you could have determined that that cost would be
106% (100% + 6%) of the price.
1.06 x $112 = $118.72
5 Minute Check
Complete on the back of your homework.
3. Your bill at a restaurant is $25.60. You want to leave a
15% tip. How much money do you need for the entire bill?
5 Minute Check
Complete on the back of your homework.
3. Your bill at a restaurant is $25.60. You want to leave a
15% tip. How much money do you need for the entire bill?
.15 x $25.60 = $3.84
This is the tip
$25.60 + $3.84 = $29.44
Or you could have determined that your total bill would be
115%.
1.15 x $25.60 = $29.44
Binder
Organization
Wednesday, Oct 2
Lesson 2.8
Solve Percent Problems
Solve Percent Problems
Objective: To solve percent problems
involving finding the whole or part.
Solve Percent Problems
Solve Percent Problems
At the end of this lesson you should be able
to answer the following questions.
How can you use proportions to solve the
percent problems?
Solve Percent Problems
A proportion is when two fractions are
equivalent.
We can solve percent problems by setting up a
proportion.
Solve Percent Problems
10 is 25% of what number?
In other words,
25% of what number is 10, or
25% of ? is 10, or
Solve Percent Problems
10 is 25% of what number?
parts
25
10
100
?
wholes
Method 1 (can be used on all questions)
Step 1 – Set up the proportion, with the
“parts” on top and the “wholes” on the
bottom.
=
Solve Percent Problems
10 is 25% of what number?
1
4
=
10
?
Method 1
Step 2 – Simplify.
Solve Percent Problems
10 is 25% of what number?
1
4
=
10
?
Method 1
Step 3 – Cross multiply and divide.
4 x 10 = 40 ÷ 1 = 40
Solve Percent Problems
30 is 50% of what number?
Step 1?
Solve Percent Problems
30 is 50% of what number?
50
100
=
Step 2?
30
?
Solve Percent Problems
30 is 50% of what number?
1
2
=
30
?
Step 3 ?
Solve Percent Problems
30 is 50% of what number?
1
2
=
30
?
2 x 30 = 60 ÷ 1 = 60
Solve Percent Problems
90 is 75% of what number?
Step 1 ?
Solve Percent Problems
90 is 75% of what number?
75
100
=
Step 2 ?
90
?
Solve Percent Problems
90 is 75% of what number?
75
90
100 = ?
3
4
=
90
?
Step 3?
Solve Percent Problems
90 is 75% of what number?
75
90
100 = ?
3
4
=
90
?
4 x 90 = 360 ÷ 3 = 120
Solve Percent Problems
60 is 20% of what number?
Method 2 (can only be used when there is a
“percent” in the question)
Step 1 – Convert the percent to a decimal.
20% = .2
Solve Percent Problems
60 is 20% of what number?
Method 2
Step 2 – Divide the number by the decimal.
20% = .2
60 ÷ .2 = 300
Solve Percent Problems
10 is 40% of what number?
(Do this on your own)
Solve Percent Problems
10 is 40% of what number? 25
Method 1
40
10
100
?
=
2
5
=
10
?
5 x 10 = 50 ÷ 2 = 25
Solve Percent Problems
10 is 40% of what number? 25
Method 2
40% = .4
10 ÷ .4 = 25
If you got 4, what did you do?
Solve Percent Problems
10 is 40% of what number? 25
Either you set up your proportion incorrectly,
(the number on bottom instead of on top)
Or you determined 40% of 10 (.4 x 10 = 4),
which was not what was being asked.
Solve Percent Problems
What number is 40% of 60?
(Do this on your own)
Solve Percent Problems
What number is 40% of 60?
Anytime the question asks for a percent of a
number, you just multiply.
40% of 60 =
.4 x 60 = 24
Solve Percent Problems
What percent of 120 is 120?
(Do this on your own)
Solve Percent Problems
What percent of 120 is 120?
Since we have no percent in the question, we
have to use method 1.
?
100
?
100
=
120
120
=
120
120
Since the answer is a
percent, the ? must be in the
“percent” fraction.
100 x 120 = 1200 ÷ 120 = 100%
Solve Percent Problems
What percent of 600 is 12?
(Do this on your own)
Solve Percent Problems
What percent of 600 is 12?
?
100
?
100
=
12
600
=
1
50
2nd number in the question
1st number in the question
100 x 1 = 100 ÷ 50 = 2%
Solve Percent Problems
40 is 20% of what number?
(Do this on your own)
Solve Percent Problems
40 is 20% of what number?
If you have a
Method 1
calculator, you can
20
40
multiply then divide the
100
?
=
1
5
=
40
?
“unsimplified” fraction.
5 x 40 = 200 ÷ 1 = 200
Solve Percent Problems
40 is 20% of what number?
Method 2
20% = .2
40 ÷ .2 = 200
Solve Percent Problems
What percent of 300 is 45?
(Do this on your own)
Solve Percent Problems
What percent of 300 is 45?
Since there is no “percent” number in the question, we have
to use method 1.
?
100
?
100
=
45
300
=
3
20
2nd number in the question
1st number in the question
100 x 3 = 300 ÷ 20 = 15
Solve Percent Problems
Molly has $10 in her wallet. If this is 20% of her
monthly allowance, what is her monthly
allowance?
(Do this on your own)
Solve Percent Problems
Molly has $10 in her wallet. If this is 20% of her
monthly allowance, what is her monthly allowance?
Method 1
20
10
100
?
=
1
5
=
10
?
10 x 5 = 50 ÷ 1 = 50
2 (.2 x 10 ) is not the correct answer
Solve Percent Problems
Molly has $10 in her wallet. If this is 20% of her
monthly allowance, what is her monthly
allowance?
Method 2
20% = .2
10 ÷ .2 = 50
Solve Percent Problems
Agenda Notes
Homework – Homework Practice 2-8
Due Thursday, Oct 3
Circle your answers
Chapter 2 Test-Friday, Oct 4
Due to conferences, no help session this
chapter.