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

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number of trials

Example :

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?

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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°

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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

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