Introduction to Percent

1. • 1. Review: Ratio/Proportion
• 2. Discuss Ratio/Proportion Quiz
• 3. Introduction to Percent
– The Basics
• 4. The Percent Statement
• NO CLASS MONDAY

2. • Percent means “out of 100”
400 400
• So, if you get 4 out of 5
questions right on a
quiz, we generally give a
You can see these two fractions
percent to show a grade.
are equal, by multiplying
diagonally.
• Percentage is a way of
putting numbers in the
same terms so no matter Because of this relationship, you
what you compare, an can set up a proportion to
understanding can me calculate percentage, find the
made. part, or find the whole.

3. • You will need to know how to
convert:
–A decimal to a fraction (place value)
–A fraction to a decimal (division)
–A fraction to a percent (division)
–A percent to a fraction or decimal
(place value/division)

4. • 1. Drop the percent
sign (%).
.45.%
.
Percent Decimal
45% 0.45
8% 0.08
37 ½ % 0.37 ½ or 0.375
• 2. Move the decimal 250% 2.5
point two places to the
LEFT.

5. • Change 35 % to a
• 1. Drop the %
fraction.
sign.
• 2. Write 100 as •
the denominator.
• 3. Reduce. • Common denominator
=5

6. • 1. Drop the % sign. • Change 16 2/3 % to a
fraction.
• 2. Change to an
improper fraction. %
• 3. Multiply by 1
• 4. Reduce. 2

7. Percent Part
15% of $25 is $3.75
Whole
Part Whole
$3.75 is 15% of $25
Percent
You will be asked to find the part, the percent, or the whole.

8. • Two Strategies:
• 1. Turn the percent into a decimal and then
multiply.
• Ex) Find 25% of 12.
• .25 x 12 = 3
• 3 is 25 % of 12.

9. This relationship is ALWAYS TRUE.
Step 1: Write a
Josh got 4 out of 5
proportion statement.
questions right on a
test. What is his
percentage?
Step 2: Find the cross
Step 3: Divide by 5
products.
on both sides.
4 is the part.
5 is the whole.
We are looking for
the %.

10. • Find 25% of 12.
•Step 1: Set up a
proportion.
•Step 2: Cross multiply.
•Step 3: Divide

11. • Option 1: Change
the percent to a
decimal, then
multiply.

12. • Option 2: Write a
proportion
statement.

13. • A state official predicts that 70% of the registered voters in
Montana will vote on election day. If there are 514,000
registered voters in Montana, how many are predicted to
vote?
Step 1: Understand the
question. “How many
registered voters are
predicted to vote?”
Step 2: What info do
you need? Use the % of
voters predicted to vote
and the number of
registered voters.
Step 3: Choose the
operation. What is 70%
of 514,000?

14. • 6. Randi’s property tax bill is increasing by 3%
this coming year. She now pays $890 a year in
property tax.
• A) By how much is her property tax going to
increase?

15. • 6. Randi’s property tax bill is increasing by 3%
this coming year. She now pays $890 a year in
property tax.
• B) How much will she pay next year?

17. • 1. First make a • 27 is what percent
fraction. Put the of 45?
part (is) over the
whole (of) and
reduce.
• 2. Change the
fraction to a percent.

18. • Use the calculator to
find what percent 27 is
of 45.
1. Press AC
2. Press 2 7 ÷ 4 5 SHIFT %
The display should read 60.
The answer is 60%.

19. • 1. 9 is what percent of • 7. The Melino family
36? was on vacation for 12
days. It rained 3 of
those days. On what
percent of their
• 7 is what percent of 35? vacation days did it
rain?

20. • 1. Change the • 20% of what is 9?
percent to either a
fraction or a decimal.
• 2. Divide the number
by that fraction or
decimal.

21. • Use the calculator to
find 20% of what
number is 9.
1. Press AC
2. Press 9 ÷ 2 0 SHIFT %
The display should read 45.

22. • 1. 18 is 50% of what • 6. Paul and Jane
number? Bidwell pay $150 a
month on their car
loan. This is 5% of
their monthly
• 25% of what income. How much
number is 30? do they make each
month?

23. •P stands for the Part
•% stands for the Percent
P •W stands for the WHOLE
•The line
means by.
% x W •The X means multiplied
by

24. To Use the Percent
P Circle:
1. Cover the symbol of
the number you are
looking for.
% x W 2. Do the math shown
by the uncovered
symbols.

25. What is 50% of 8?
P
% x W

26. 4 is 50% of what
number?
P
% x W

27. • To find a percent of a • What is 62 ½ % of 56?
number:
• Decimal
• Step 1: Change the • 62.5 x 56 = 3500
percent to a decimal or
a fraction.
• Move decimal two
places to the left.
• Step 2: Multiply
• 62 ½ % of 56 is 35.

28. • To find a percent of a • What is 62 ½ % of 56?
number: • Fraction
• Step 1: Change the
percent to a decimal or
a fraction.
• Step 2: Multiply

29. • To find the part: • 27 is what percent of
• 1. First make a fraction. 45?
Put the part over the
whole and reduce.
• 2. Change the fraction
to a percent.

30. • The Melino family was • Write the fraction as
on vacation for 12 days.
It rained 3 of those
days. On what percent
of their vacation did it • Change the fraction to
rain? percent.
•

31. • 1. Change the percent • 20% of what number is
to either a fraction or a 9?
decimal.
• Change to a fraction
• 2. Divide the number
by that fraction or
decimal.

32. Percent Part
15% of $25 is $3.75
Whole
Part Whole
$3.75 is 15% of $25
Percent

33. • Mrs. Jackson makes $450 is her total income.
a week. She pays
$90 a week for She spends $90 on food.
food. Money spent
for food is what $90 is what percent of $450?
percent of her
income?

34. • 60% of what
number is 45?
• Lois got a 6%
commission for
selling a house. She
sold a house for
$120,000. Find the
commission.

35. •P stands for the Part
•% stands for the Percent
P •W stands for the WHOLE
•The line
means by.
% x W •The X means multiplied
by

36. To Use the Percent
P Circle:
1. Cover the symbol of
the number you are
looking for.
% x W 2. Do the math shown
by the uncovered
symbols.

37. What is 50% of 8?
P
% x W

38. 4 is 50% of what
number?
P
% x W

39. • Sally wants a new computer that costs $900.
She has saved 75% of the price. How much
has she saved?
I am looking for the part.
P
%xW .75 x $900 = $675

40. • Bill paid $2 sales tax on a $40 shirt. The tax
was what percent of the list price?
I am looking for the percent.
P
%xW
2/40= 1/20=.05
5%