Percent Change
Aim: To calculate "Percent of Change" (729)
Homework: Worksheet (see website)
When a quantity increases, it increases by a quantity and by a
percent.
Warm Up:
The change in the percent is known as the percent increase or
decrease
Daniel weighs 190 pounds. Miriam guessed his weight and guessed 110
pounds. What is the percentage that Miriam got wrong? Round your
answer to the nearest tenth of a percent.
For example, when there is a change from 40 to 60, it is a
quantity change of 20 and a percent chance of 50%.
Formula to find the Percent Increase or Decrease:
MODEL
Find the percent increase or decrease from 24 to 26
Quantity change:
Change in Quantity
Original Amount
x 100
Original:
Formula:
Change in Quantity
Original Amount
x 100
(we multiply by 100 to change it to a percent)
• If a number doubles, it's change is 100%
example: 50 to 100
What is the percent increase if the original value of 60 increases by 30?
Quantity change:
• If a number increases by half it's amount, it's change is 50%
example: 60 to 90
Original:
• If a number TRIPLES, it increases by 200%, quadruples, 300%, etc.
example: 50 to 150
TRY IT
Find the percent increase or decrease from $212 to $90
Quantity change:
Original:
Formula:
Change in Quantity
Original Amount
x 100
1 Pre Activity Assessment: A contestant on the biggest
loser originally weighed 200 pounds and now weighs 160
pounds. Calculate the percent change.
A 20%
B 25%
C 40%
D 400%
Percent Change
Application- Find the percent of change for each. State whether it
is an increase or decrease. Move to next task when complete.
A) Find the percent of change if an item which originally sold at $25 was reduced to $20.
B) A car runs at 55 mph. Twenty minutes later the cars speed
increased to 63 mph. Ten minutes later the cars speed dropped to
59 mph. Compute the cars percent of change for each. Between
which 2 intervals did the cars speed change the most?
C) A home owner decides to sell his house and lists the price for
$449,900. One buyer offers $435,000 while another offers
$440,500. Calculate the percent change between the 2 offers.
H.O.T.:
At#a#student#council#mee/ng,#there#were#a#total#of#60 students#present.#Of#those#
students,#35 were#female.#
a)#By#what#percent#is#the#number#of#females#greater#than#the#number#of#males?
b)##By#what#percent#is#the#number#of#males#less#than#the#number#of#females?
Percent Change
Summary: Find the percent change from 200 to 400 mentally. Explain how you
determined your answer.
Questioning for Assessment/Student Progress
*Recite the steps needed to find the percent of change.
*What alternate methods can be used to calculate the percent of
change? Proportions,etc.
*How do we identify an increase or decreased changed?
*Why do we multiply by 100?
*Describe the next step needed to solve for the percent of change.
*How might this lesson connect to the real-world?
*Explain how this may be relevant to someone in retail.
*Extrapolate our next class lesson/topic.