1.finding percenatages 1.percentage increase & decrease week 4
TRANSCRIPT
1. Finding Percenatages
1. Percentage increase & decrease
WEEK 4
STARTER
1. {x : x is even and x ≤ 8}
1. {x : x = 3n, n ∈ N, n ≤ 4}
1. {x : x = n2, n ≤ 5, n ∈ N}
1. {x : x is odd}
On your notebook, write the following sets in the ROSTER NOTATION.
STARTER ANSWERS
1. A = {2, 4, 6, 8}
1. B = {3, 9, 27, 81}
1. C = {1, 4, 9, 16, 25}
1. D = {1, 3, 5, ......}
OBJECTIVES
1. Find percentages of quantities
2. Interpret percentage as an operator.
3. Use a multiplier to increase or decrease.
What is a percentage?
What is a percentage?
A percentage is a ratio of a number to 100.
The symbol % is used to indicate a percent.
The word percent means “per cent” , “per hundred.” So 6% means “6 out of 100.”
7100
= 7 %
Example
Notice the 10 x 10 square grid. There are 100 total squares. Seven of the squares are colored. Seven red squares of 100 total squares can be shown like this:
Which of the following is an example of a percent?
23%A B67
Write the percent modeled by each grid.
A. B.
Example 1: Modeling Percentage
shaded total
_______ 32100
___ = 32% shaded total
_______ 75100
___ = 75%
Steps
Write the percent modeled by each grid.
A. B.
Example 2: Modeling Percentage
shaded total
_______ 44100
___ = 44% shaded total
_______ 66100
___ = 66%
Steps
Additional Example 3: Writing Percentage as Decimals
Write 21% as a decimal.
Method 1
Use pencil and paper.
21% = 21100
= 0.21
Write the percent as a fraction with a denominator of 100.
Divide 21 by 100.
Method 2 Use mental math.
21% = 0.21 Move the decimal point two places to the left.
I do: How did I calculate the percent to a decimal?
Finding Percentages of a number!
Example 1:34% of 5 = (34/100) x 5 = 1.7
Example 2:6% of 1.45= (6/100) x 1.45= 0.087
Example 1:21% of 650 AED = (21/100) x 650 = 136.5 AED
Example 2:85% of 38 KG= (85/100) x 38= 32.3 KG
Example 3:Find 3½% of $80First > Express (7/2)/100 as a fraction = 7/200 = 0.035Second > (0.035) x (80) = 80/15 = $2.80
Finding Percentages of quantities?
Increasing and Decreasing Quantities by a PercentageWhen increasing or decreasing by a percentage, there are two ways to do this: 1.Find the actual increase or decrease and add it to, subtract it from the original amount. 2.Use a simple multiplication
For example, to increase by 20%, multiply by 1.2. We increase an amount (b AED) by 20%.
The increase is b AED x (20/100) = 0.2 bSo the new price is b AED + 0.2b = (1 + 0.2)b = 1.2b
A 20% increase is the same as to multiply by 1.2 to get the new price. 100% + 20% = 120% = 120/100 = 1.2 1.2 is the multiplier!
A 20% decrease of 20% is the same as:100% - 20% = 80% = 80/100 = 0.8 0.8 is the multiplier!
What is a multiplier? How does it help to increase and decrease the change in percentage?
Example question 1 - Increase AED130 by 20%. An increase of 20% is an increase from 100% to 120%.
To do this you would multiply by 120/100, which is the same as multiplying by 1.2.
In other words, multiplying an amount by 1.2 is the same as increasing it by 20%.
So the number 1.2 is the multiplier needed to do the calculation, which now looks like this: AED 130 x 1.2 = AED156, which is the answer.
Teacher to go over Example 4.4 & 4.5 (Maths iBook page 72 & 73)
CLASSWORK 1 Pair Activity
On your notebook, show an organized
solution on the following:
G11 Mathematics Website
WK 4 – L1 CLASSWORK 1 IGCSE Past
Paper Questions on Percentage
CLASSWORK 2 Individul Activity
On your notebook, show an organized
solution on the following:
iBook G11 Maths, page 75 – 76
#’s 1, 2, 3 a, c, f, h, 4, 5, 6
HOMEWORK
On your notebook, show an organized
solution on the following:
1. iBook G11 Maths, page 76 #’s 7 & 8
2. Any classwork NOT finished
EXTENSION ACTIVITY
For advanced students:
On your notebook, show an organized
solution on the following:
G11 Mathematics Website
WK 4 – L1 Extension Activity 1 Percentage
PLENARY
Share one or two things you have learned
in today’s lesson
THANK YOU!