Useful Formulae

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Multiplying Intergers

Rules For Multiplying Intergers

  • Positive x Positive = Positive 
  • Positive x Negative = Negavite 
  • Negative x  Negative = Positive 
  • Negative x Positive = Negative
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Dividing Intergers

Rules For Dividing Intergers

  • Positive ÷ Positive = Positive
  • Positive ÷ Negative = Negative
  • Negative ÷ Negative = Positive 
  • Negatve ÷ Positive = Negative
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Probability

Rules For Probability

  • Probability of an outcome =

number of ways an outcome can happen

total number of possible outcomes

  • Sum of probabilities of mutually exclusive outcomes = 1
  • Estimate of number number of sucesses = probability of sucess x number of trials
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Mean

Rules For Mean

The mean is the total of numbers divided by how many numbers there are.

1. Add up all the numbers 

2. Divide the answer by how many numbers there are

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Mode

Mode

The number that appears the most 

e.g {6, 3, 9, 6, 6, 5, 9, 3} the Mode is 6 (it occurs most often)

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Median

Rules For Median

The median is the middle value

1. Put the numbers in order smallest - biggest

2. Look for the middle number, that will be your median

3. If there is two middle numbers, the number is halfway between them

e.g. 3 6 6 6 7 8 9 11 11 13. There are two middle numbers 7 and 8 therefore the median will be 7.5

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Range

Rules For Range

The range is the difference between the smallest and largest number

1. Put the numbers in order

2. Subtract the smallest number from the biggest number

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Areas

Rules For Area

  • Rectangle = Length x Width
  • Parallelogram = Base x Height
  • Triangle = 1/2 Base x Height
  • Trapezium = 1/2 (a+b) h
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Volumes

Rules For Volumes

  • Cuboid = Length x Width x Height
  • Prism = Area of triangle x Length
  • Cylinder = Pi r2 x Height
  • Pyramid = 1/3 x Area of base x Height
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Circles

Rules Of Circles

  • Circumference = Pi x Diameter, C = Pi d
  • Circumference = 2 x Pi x Radius, C = 2 Pi r
  • Area of a circle = Pi x Radius squared A = Pi r 2 
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Compound Measures

Rules For Compound Measures

  • Speed = Distance ÷ Time
  • Distance = Speed x Time 
  • Time = Distance ÷ Speed
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Pythagoras

Rules For Pythagoras 

  • Pythagoras' therom - right angle triangle = a2 + b2 = c2 
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