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!