# Year 9 - Maths Revision

Probability :

- Sample space diagram

- Venn Diagram

- Frequency trees

- Relative frequency/experimental probability

Percentages :

- percentage of an amount

- percentage increase/decrease

- reverse percentage

- percentage change

- expressing one number as a percentage of another

Angles :

- angles in parallel lines

- angles in polygons

- interior and exterior angles

Formulae :

- Rearranging formulae - one/two step

- Rearranging formulae involving factorising

Probability :

- Sample space diagram

Hegarty maths clip/s : 359 - Probability of more than one event (2)

- Venn Diagram

Hegarty maths clip/s : 378-391 (all to do with Venn diagrams)

! NOTE ! if they ask you to draw a Venn diagram, you must include the box around the circles as it is part of the diagram.

- Frequency trees

Hegarty Maths clip/s : 368-369 : Frequency Trees

- Relative frequency/experimental probability

Hegarty maths clip/s : 356 - Experimental probability & relative frequency

Relative frequency = number of successes

-------------------------------------

number of trials

Example :

cars

vans

other

60

21

3

Relative frequency = 21/ 84 = 0.25

Percentages :

- percentage of an amount

example :

30 % of 100 = 30

10 % = (100 / 10) 10

30% = 10% x 3

- percentage increase/decrease

example :

decrease 100 by 30%

30% = 30

100 (100%) - 30 (30%) = 70

- reverse percentage

- percentage change

Example:

The population of birds on an island in 2017 was 2500.

The population of the birds was 2155 in 2018.

What is the percentage decrease of the population?

1. find the ‘change’

2500-2155=345

2. 345/2500 x 100 = 13.8

- expressing one number as a percentage of another

Angles :

- angles in parallel lines

- angles in polygons

All the interior angles in a regular polygon are equal. The formula for calculating the size of an interior angle is: interior angle of a polygon = sum of interior angles ÷ number of sides. The sum of exterior angles of a polygon is 360°

formula = n - 2 x 180°

n = number of sides

Example :

what’s the interior angles add up to in a 5 - sided polygon?

5-2 = 3

3x 180 = 540°

540°

- interior and exterior angles

Formulae :

- Rearranging formulae - one/two step

Example :

9x+2=29

29-2=27

27/9=3

x=3

- Rearranging formulae involving factorising

Example :

5m - 4m = -12y - 5y

1m/1 = -12y - 5y/1

m = -12y-5y/1 = 17y

m=17y