maths 2

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  • Created by: natalie
  • Created on: 19-02-15 09:31

discrete and continuos data

Discrete data is like a pair of shoes size 4 and 5 are ok but size 4.3 is no use, no in between numbers.

Continous data is like measurements. they have in between points 0.1 0.2

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Percentage

10% move one dp to the left

on a calculator number divided by 100 x 10%

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Simple Interest

Divide the interest by he amount of the loan (other money number) and then x by 100.

Lucy has aloan of £750 she pays interest of £25.50 per month. What is the rate of a simple interest.

£25.50 divide by £750 = 0.034

Then times 0.034 by 100

Answer 3.4%

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Percentage increase and decrease

% of an amount divided by 100 x amount =

There is a sle in top shop and your favourite jeans are 56% off they cost £20 originally

eg 4% of 920

4 divide by 100 x by 920

WORKING OUT THE PERCENTAGE RATE

Numberdivide by Number x 100- So the other way around!

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Percentage Original Amount

If a dress cost £42 in the sale it was reduced by 15% what was the original price?

You need the whole information is 100% 

Take the percentage you have been given away from 100 so in this example 100- 15% = 0.85

Then

Divide the price or number by your percentage

42 divided by 0.85 = £49.41

The amount should be bigger!

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Factorising expressions

2x+6 becomes 2(x+3)

2x-24 becomes 2(x-12)

6n-48 becomes 6(n-8)

3+3t becomes 3(1+t)

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Polygons

To find number of triangles in a ploygon shape - take 2 away from the number of sides in that shape

Sum of interior angles =

times the number of triangles by 180 degrees

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sums of each interior and exterior angle

Sum of each exterior angle=

To find the size of each exterior angle, we divide the sum

of the interior angles by the number of sides. Then take

that number from 180 degrees.

Sum of each interior angle= 

We divide the sum of interior angles by the number of

angles in the shape. 

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Pythagoras theory

To work out the longest side 

Square both of the other side seperatley anf then add them together

Then find square root

To work out the shortest side

the point of the right angle points to the shortest side

so square both of the sides seperatley but take away from each other

Then find sqaure root

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Dividing Fractions and whole numbers

3 divide by 1/2

Make the whole number into a fraction with denominator as 1

3/1

the swap the other fraction around, so denominator becomes numerator

2/1

multiply your numbers then simplify if you can

3/1 x 2/1 = 6/1

Simplified =6

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Decimals to fractions, fractions to decimals

DECIMAL TO FRACTION:

0.6=6/10    0.4= 4/10    0.65= 65/100   0.875= 875/1000

FRACTIONS TO DECIMALS

Divide the numerator by the denominator (with a calculator) or multiply the fraction by 1.00 eg. 

2/5x1.00= 2 x 1.00 = 2.00 = 0.40 or .04

                5 x1.00        5

the 2.00 has been changed to 200 then dp added

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