Percentage increase and decrease bell
ringers
On a loose leaf sheet write your name, block, and title.
Answer the following percentage problems by using ratios.
Show your work. This will be graded. Turn in when complete.
At the animal shelter there were 𝟏𝟓 dogs, 𝟏𝟐 cats, 𝟑
snakes, and 𝟓 parakeets.
1. What percent of cats are at the animal shelter?
2. What percent of dogs are at the animal shelter?
3. What percent of snakes are at the animal shelter?
4. What percent of parakeets are at the animal
shelter?
7.RP.3 Percentage Increase and
Decrease
Created by: Melissa Forsyth
How is displaying change as a percent
useful?
Percent increase and percent decrease are
measures of percent change, which is the extent
to which something gains or loses value. Percent
changes are useful to help people understand
changes in a value over time. Representing
change as a percent helps us to understand how
large the change is compared to the whole.
Created by Melissa Forsyth
Cassandra likes jewelry. She has five rings in her
jewelry box.
1. What percent is represented by the whole collection of rings? What percent of the
collection does each ring represent?
Created by Melissa Forsyth
Calculating Percent Increase: with unknown percent
Cassandra’s aunt said she will buy Cassandra another ring for
her birthday. If Cassandra gets the ring for her birthday, what
will be the percent increase in her ring collection?
One way we can find the percent increase by writing our sentence:
Percent of whole = new part or Percent x whole = new part
Since we do not know the percent we will call it p.
P x 5 rings(whole) = 1 new ring(part)
Isolate P by Dividing
5𝑃 1
=
5
5
P = .2
Multiply by 100 to find percent.
.2 x 100 = 20%
20% represents one ring, so her ring collection would increase by 20%.
Created by Melissa Forsyth
Calculating Percent Increase: with unknown percent
Cassandra’s aunt said she will buy Cassandra another ring for her
birthday. If Cassandra gets the ring for her birthday, what will be
the percent increase in her ring collection?
When finding the percent increase, we take the absolute value of the difference
and divide it by the original value. The resulting decimal is then converted to a
percent.
𝑛𝑒𝑤 𝑤ℎ𝑜𝑙𝑒 −𝑜𝑙𝑑 𝑤ℎ𝑜𝑙𝑒
𝑤ℎ𝑜𝑙𝑒
= decimal
Decimal x 100 = percent
• BE VERY CAREFUL WITH USING THE FORMULA NOT TO MIX UP THE PARTS
AND NEW WHOLE. ALSO BE VERY CAREFUL THAT YOU ALWAYS DIVIDE BY THE
ORIGINAL WHOLE.
The part would be 1, but the new whole would be the part + the original whole.
l 6 − 5I
5
=
l1l
5
1 ÷ 5 = .2
.2 x 100 = 20%
1
=5
Created by Melissa Forsyth
Calculating Percent Increase:
unknown percent
Jon increased his trading card collection by 𝟓
cards. He originally had 𝟏𝟓 cards. What is the
percent increase? Write your sentence and
solve.
5 = p x 15
5
15
1
3
=
15𝑝
15
=𝑝
1 ÷ 3 = .33 repeating
1
.3333 x 100 = 33 3 %
Created by Melissa Forsyth
Calculating Percent Increase:
Unknown Percent
Your dog go nuts and eats the entire bag of dog
food and goes from 110 pounds to 125 pounds.
What was his percentage weight gain?
Created by Melissa Forsyth
Calculating Percent Increase:
Unknown Percent
Ann works in a supermarket for $10.00 per hour.
If her pay is increased to $12.00, then what is
her percent increase in pay?
Created by Melissa Forsyth
Calculating Percent Increase:
Unknown Percent
At a supermarket, a certain item has increased
from 75 cents per pound to 81 cents per pound.
What is the percent increase in the cost of the
item?
Created by Melissa Forsyth
Calculating percent increase: New Part Unknown
Growing up, you lived in a tiny country village. When you left
for college, the population was 840. You recently heard that
the population has grown by 5%. What is the present
population?
• BE CAREFUL WITH PERCENT INCREASE PROBLEMS. YOU WILL BE TEMPTED TO
JUST USE THE 5% AS YOUR PERCENTAGE, BUT THIS 5% IS ONLY THE INCREASE OF
PERCENT, YOU MUST ALSO INCLUDE THE 100% THAT SHOWS THE WHOLE.
1. Write your sentence.
% x whole = part
100% + 5% x 840 = part
105% x 840 = part
2. Change your percentage into a decimal.
105 ÷ 100 = 1.05
3. Multiply your decimal by the whole.
1.05 x 840 = 882
882 people currently live in the tiny country village.
Created by Melissa Forsyth
Calculating percent increase: New Part Unknown
Growing up, you lived in a tiny country village. When you left
for college, the population was 840. You recently heard that
the population has grown by 5%. What is the present
population?
First we have to identify the part percent: to find this we have to add the increase
of percent to 100.
100 + 5 = 105.
Next we have to insert our numbers into our ratio.
105%
100%
𝑥
= 840
Cross Multiply: 100x = 88200
Isolate x by dividing.
100𝑥 88200
= 100
100
X = 882
Created by Melissa Forsyth
Calculating percent increase: New Part Unknown
Growing up, you lived in a tiny country village.
When you left for college, the population was 840.
You recently heard that the population has grown
by 5%. What is the present population?
First, find the actual amount of the increase.
Since the increase is five percent of the original, we first change the percent into a
decimal. We then multiply that decimal by the whole, this will give us our new part.
(0.05)(840) = 42(the number of new people)
To find the new amount of total people we simply add the number of old people and the
number of new people.
840 + 42 = 882 people currently living in the village.
Created by Melissa Forsyth
Calculating Percent Increase: New
Part Unknown.
The number of visitors to the peanut festival in 2015 was 12,350
and visitation is expected to increase by 35% in 2016, how
many visitors will attend the peanut festival in 2016?
Created by Melissa Forsyth
Calculating Percent Increase: New
Part Unknown.
Tom was paid 24.99 an hour in 2015. If his pay increases 12%
each year, how much will he be paid in 2016?
Created by Melissa Forsyth
Calculating Percent Increase: New
Part Unknown.
In an average month a grocery store sells 1350 packs of bottled
water. A hurricane is predicted to hit the small town in which
the grocery store is located and bottled water sales are
predicted to increase 55%. How many packs of bottled water is
the grocery store predicted to sell?
Created by Melissa Forsyth
Calculating Percent Increase: New
Part Unknown.
The price of an C3PO in 1972 was $15.99. With a resurgence in
interest in the Star Wars movies recently the same figurine’s
value increased by 110%. How much is the figurine currently
worth?
Created by Melissa Forsyth
Calculating Percent Increase: Original
Whole Unknown.
A pet store increased its sales 30% in the year 2015 to 47,500 a
month. How much did the pet store earn prior to the increase
in sales.
To calculate the original whole first you must write your sentence.
Percent (100% + percent increase) x whole = new whole
Convert the percent into a decimal
1.30 x W = 47,500
1.30W = 47,500
Isolate the W by dividing
𝟏.𝟑𝟎𝑾 𝟒𝟕,𝟓𝟎𝟎
= 𝟏.𝟑𝟎
𝟏.𝟑𝟎
𝐖 = $36,538.46 in original earnings
Created by Melissa Forsyth
Calculating Percent Increase: Original
Whole Unknown.
A dog shelter took in an additional 6 dogs and this increased
the dog food consumption by 25%. If they currently use 840
pounds of dog food in a month with the increase, how much
dog food was consumed prior to taking in the additional dogs.
Created by Melissa Forsyth
Calculating Percent Increase: Original
Whole Unknown.
Isaiah’s baseball card collection is currently worth $4,600 which
was an increase of 23% from what he originally paid. How much
did Isaiah pay for his baseball card collection?
Created by Melissa Forsyth
Calculating Percent Increase: Original
Whole Unknown.
With the draught sweeping the state my average water
consumption increased by 45% and now we are using 840
gallons of water a month. What was my household using prior
to the draught?
Created by Melissa Forsyth
Calculating Percent Increase: Original
Whole Unknown.
When racing a dirt bike the gas consumption increases 8% to 22
miles per gallon. How many miles per gallon will a dirt bike get
if it is not racing?
Created by Melissa Forsyth
Percent increase vs. percent decrease
In percent increase problems, the final value or
quantity is greater than the original value or
quantity; therefore, it is greater than 100% of
the original value or quantity.
In percent decrease problems, the final value is
less than the original value or quantity;
therefore, it is less than 100% of the original
value or quantity.
Created by Melissa Forsyth
Percent Decrease
“A sales representative is taking 10% off of your
bill as an apology for any inconveniences”.
What does this statement mean?
I will only pay 90% of my bill.
or
10% of my bill will be subtracted from the original total.
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown New Whole
Ken said that he is going to reduce the number of calories
that he eats during the day. Ken’s trainer asked him to start
off small and reduce the number of calories by no more than
𝟕%. Ken normally consumes 𝟐,𝟓𝟎𝟎 calories per day. How
many calories should Ken eat.
To calculate percent decrease we need to write a sentence.
(100% - percent decrease) x original whole = new whole.
100% - 7% x 2,500 = N
Convert the percent into a decimal and solve equation
93% x 2,500 = N
.93 x 2,500 = N
N = 2,325
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown New Whole
Ken said that he is going to reduce the number of calories
that he eats during the day. Ken’s trainer asked him to start
off small and reduce the number of calories by no more than
𝟕%. Ken normally consumes 𝟐,𝟓𝟎𝟎 calories per day. How
many calories should Ken eat.
To calculate percent decrease we need to write a sentence.
Percent x whole = part
7% x 2,500 = part
Convert the percent into a decimal and solve equation
7% x 2,500 = part
.07 x 2,500 = part
Part = 175
Subtract the original whole and the part to find the new whole.
2,500 – 175 = 2,325
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown New Whole
Ken said that he is going to reduce the number of calories
that he eats during the day. Ken’s trainer asked him to start
off small and reduce the number of calories by no more than
𝟕%. Ken normally consumes 𝟐,𝟓𝟎𝟎 calories per day. How
many calories should Ken eat.
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown New Whole
A store advertises 𝟏𝟓% off an item that regularly sells
for $𝟑𝟎𝟎. What is the sale price of the item?
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown New Whole
The pet store is having a sale on exotic pets. All
exotic pets are 18% off. If a Macaw costs $475,
approximately how much will the Macaw cost
after the sale?
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Percent
An item that was selling for $𝟕𝟐 is reduced to $𝟔𝟎.
Find the percent decrease in price. Round your answer
to the nearest tenth.
To find the percent decrease you use the following formula:
𝒐𝒓𝒊𝒈𝒊𝒏𝒂𝒍 𝒑𝒓𝒊𝒄𝒆 −𝒏𝒆𝒘 𝒑𝒓𝒊𝒄𝒆
𝒐𝒓𝒊𝒈𝒊𝒏𝒂𝒍 𝒑𝒓𝒊𝒄𝒆
= decimal
Decimal x 100 = percent decrease
$𝟕𝟐 −$𝟔𝟎
$𝟕𝟐
$𝟏𝟐
= $𝟕𝟐 = .16 repeating
.1666 x 100 = 16.66%
16.7%
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Percent
If a Chevy Aveo originally sells for 16,000 and is
now on sale for 12,500. Approximately what
percentage of the cost was taken off?
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Percent
If a pack of diapers costs $45 originally but on
black Friday they are on sale for $36. How much
percent off were the diapers?
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Percent
The cost of gas in WI is $3.99 per gallon. The
cost of gas in AL is $1.69. Approximately what
percentage of decrease is the cost of gas
between the two states?
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Original whole
A new iphone 6 is on sale for 15% off and will now cost
$350. Approximately what was the original cost of the
iphone?
To calculate the original cost you will use the following formula
100% - percent decrease x original whole = new whole
100% - 15% x W = 350
85% x W = 350
Convert percentage into decimal.
.85 x W = 350
.85W = 350
Isolate the W by dividing
.85𝑤
350
=
.85
.85
W = 411.76
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Original whole
If a stove is on sale for $457 after a 35% off sale.
Approximately what was the original cost of the
stove?
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Original whole
If baby formula is on sale for 65% off per can
and the can now costs 6.59, approximately what
was the original cost of the formula?
Created by Melissa Forsyth
Calculating Percent Decrease:
Unknown Original whole
Baby bottles are on sale for 45% off. If they now
cost 7.99, approximately how much did they
originally cost?
Created by Melissa Forsyth
Practice
Justin earned 𝟖 badges in Scouts as of the Scout Master’s last
report. Justin wants to complete 𝟐 more badges so that he
will have a total of 𝟏𝟎 badges earned before the Scout
Master’s next report. If Justin completes the additional 𝟐
badges, what will be the percent increase in badges?
Created by Melissa Forsyth
Practice
The population of cats in a rural neighborhood has declined
in the past year by roughly 𝟑𝟎%. Residents hypothesize that
this is due to wild coyotes preying on the cats. The current
cat population in the neighborhood is estimated to be 𝟏𝟐.
Approximately how many cats were there originally?
Created by Melissa Forsyth
Practice
Erin wants to raise her math grade to a 95 to improve
her chances of winning a math scholarship. Her math
average for the last marking period was an 81. Erin
decides she must raise her math average by 15% to
meet her goal. Do you agree? Why or why not?
Created by Melissa Forsyth
Practice
A tank that is 40% full contains 648 gallons of
water. How many gallons are in a full tank?
Created by Melissa Forsyth
Practice
Loretta picks apples for her grandfather to make
apple cider. She brings him her cart with 420
apples. Her grandfather smiles at her and says,
“Thank you Loretta. That is 35% of the apples
that we need.” How many apples does Loretta’s
grandfather needs.
Created by Melissa Forsyth
Practice
Emilio paid $𝟐𝟖𝟕.𝟓𝟎 in taxes to the school
district that he lives in this year. This year’s
taxes were a 𝟏𝟓% increase from last year. What
did Emilio pay in school taxes last year?
Created by Melissa Forsyth
Practice
A snowmobile manufacturer claims that its
newest model is 𝟏𝟓% lighter than last year’s
model. If this year’s model weighs 𝟕𝟗𝟗 lb., how
much did last year’s model weigh?
Created by Melissa Forsyth
Practice
Student enrollment at a local school is
concerning the community because the
number of students has dropped to 𝟓𝟎𝟒, which
is a 𝟐𝟎% decrease from the previous year. What
was the student enrollment the previous year?
Created by Melissa Forsyth
Practice
A color of paint used to paint a race car
includes a mixture of yellow and green paint.
Scotty wants to lighten the color by increasing
the amount of yellow paint 𝟑𝟎%. If a new
mixture contains 𝟑.𝟗 liters of yellow paint, how
many liters of yellow paint did he use in the
previous mixture?
Created by Melissa Forsyth
Practice
Alexis and Tasha challenged each other to a
typing test. Alexis typed 𝟓𝟒 words in 1-minute,
which was 𝟏𝟐𝟎% of what Tasha typed. How
many words did Tasha type in 1-minute?
Created by Melissa Forsyth
Practice
Yoshi is 𝟓% taller today than she was one year
ago. Her current height is 𝟏𝟔𝟖 cm. How tall was
she one year ago?
Created by Melissa Forsyth
Practice
Toya can run one lap of the track in 𝟏 min. 𝟑
sec., which is 𝟗𝟎% of her younger sister Niki’s
time. What is Niki’s time for one lap of the
track?
Created by Melissa Forsyth
Practice
An animal shelter houses only cats and dogs,
and there are 𝟐𝟓% more cats than dogs. If
there are 𝟒𝟎 cats, how many dogs are there,
and how many animals are there total?
Created by Melissa Forsyth
Practice
Angie scored 𝟗𝟏 points on a test but only
received a 𝟔𝟓% grade on the test. How many
points were possible on the test?
Created by Melissa Forsyth