Percent of Change: The percent that a quantity changes from
the _____________________ to a _____________________. The new
amount could be an _________________________ or a
_________________________. You could use the words or use an
_________________________ or use ____________________.
THINK IT OUT: Why would you want a percent instead of just
the amount of change?
Example #1
Mary and Jane went on a
diet; Mary lost 12 pounds
and Jane lost 14 pounds.
Jane’s beginning weight was
130 pounds and Mary’s
beginning weight was 120.
Who lost more weight?
Example #2
In first period Math class 17
out of 20 students scores an
A; in 3rd period 18 out of 22
students scored an A. Which
class did better?
I would want to know the percent instead of just the quantity
because ….
Review: Changing a Fraction to a Percent
Step1: Set up the fraction
Example:
Step 2: Divide the denominator into the numerator
Example:
Step 2: Move the decimal place TWO places to the right
Example:
Example #1
Example #2
Example #3
Example #4
Percent of Increase: When the original amount goes
_____________, or _____________________.
The formula to solve is:
Percent of increase = -------------------------
Sample Problem:
Do Practice Problems on Worksheet A
Worksheet A: Percent of Increase
From 45 ft to 92 ft
57 people to 85 people
24 beanie babies to 35 beanie
babies
15 taxies to 20 taxies
From 2150 mi to 7895 mi
From $328 to $333
Before: 10 coins; After 12 coins
1994 cost $75; 1995 cost $82
Original amount 45; new amount
72
From 16 tons to 24 tons
On the first day of tryouts 62 students showed up; on the second day
the total grew to 74 students.
In 2015, Eric sold used games for $45; this year he is selling them for
$55.
Percent of Decrease: When the original amount goes
______________, or __________________________.
The formula to solve is:
Percent of Decrease = ----------------------------------------
Sample Problem:
Do Practice Problems on Worksheet B
Worksheet B: Percent of Decrease
From 94 miles to 34 miles
From 117 minutes to 101
minutes
Original Price $17.33, new price
$11.18
Nails in a bucket when from 87
down to 24
From 83 hours a week to 76
hours a week
Starting price $532.73; new price
$314.68
2016 Price $249
2017 Price $199
Original Number 22; new number
12
Before 15, after 12
Original amount 9 yards ribbons;
new amount 2.75 yards ribbons
Celina bought a used car for $1895; now the car is worth $1500
Sabrina weighed 187 pounds three months ago; she now weighs 143
pounds.
Percent Error: When an __________________ amount differs from
the ______________________ amount.
The formula to solve is:
Percent Error = -------------------------------
Do Practice Problems on Worksheet C
Worksheet C: Percent Error
Dennis wants to buy a card for his wife. Dennis calculates the
amount of the card as $4.50. The actual price is $4.00. What is
Dennis’ percent error?
Sabrina calculates that she will spend $125 at the market; she ends
up spending $138. What is Sabrina’s percent error?
You estimate that you will need 35 feet of wrapping paper, but end
up using 42 feet. What is your percent error?
You estimate that you will need 37 gallons of gas to get to California,
but end up using 20. What is your percent error?
In January Brittany estimates she will sell 700 t-shirts at her shop. At
the end of the year, she only sold 562. What is her percent error?
Jill guesses that it will take her 75 minutes to run 7 miles. She runs
that distance in 90 minutes. What is the percent error?
Sonya expected to get $75 for her birthday, but she only received
$50. What was the percent error?