# Maths Unit C

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- Created by: kirsty
- Created on: 11-06-13 11:52

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- Maths Unit C
- Direct and inverse proportion
- Inverse
- y 1/x read as 'y is inversely proportional to x'
- example y=5 when x=4 5=m/4 5x4=m=20 y=20/x
- further examples: find y when x=30 y=20/30=0.6 find x when y=25 25=20/x x=20/25=0.8

- example y=5 when x=4 5=m/4 5x4=m=20 y=20/x

- y 1/x read as 'y is inversely proportional to x'
- Direct
- y x read as 'y is directly proportional to x'
- example: y=1.8 x=9 y=mx 1.8=mx9 1.8/9=m=0.2 y=0.2x
- further examples: find y when x=52 y=0.2x52 =10.4 find x when y=42 42=0.2 * x 42/0.2=x=210

- example: y=1.8 x=9 y=mx 1.8=mx9 1.8/9=m=0.2 y=0.2x

- y x read as 'y is directly proportional to x'

- Inverse
- percentage increase and decreases
- Increase
- 100%+ (the percentage increase) then that number x by original amount
- Example: Julie is given a pay rise of 3.5% on her current salary of 34900 so: 100%+3.5%= 103.5% 34900x103.5 = 36121.50

- 100%+ (the percentage increase) then that number x by original amount
- Decrease
- 100%-(the percentage decrease) then this number x by original amount
- example: work out the new price of a camera that did cost £480 before the 22% reduction so: 100%-22%= 78% 480x0.78=£374.40

- 100%-(the percentage decrease) then this number x by original amount

- Increase
- circles
- circumferene = pie x diameter
- example= pie x 8 = 8pie= 25.13274123

- area = pie x r squared
- example pie x 4 squared = 16 pie = 50.26548246
- for sectors for both area and circumference you just do the angle of the sector divided by 360 and then the same as you did for the others.

- example pie x 4 squared = 16 pie = 50.26548246
- cherry pies delicious! apple pies are too!

- circumferene = pie x diameter
- Factorising
- examples: PQR+RST = R(PQ+ST) 4XY-8X = 4(XY-2X) 2A+2B = 2(A+2B)
- factorising a x"+4x+3=0 you would get (x+3) and (x+1) this is because the numbers add to make the middle and times to make the end number.

- expanding: 4(5a+2) = 20a +8 3x(2-9y) = 6x-9xy 3(2x+5) = 6x+15
- when cant factorise use the quadratic formula!

- examples: PQR+RST = R(PQ+ST) 4XY-8X = 4(XY-2X) 2A+2B = 2(A+2B)

- Direct and inverse proportion
- y 1/x read as 'y is inversely proportional to x'
- example y=5 when x=4 5=m/4 5x4=m=20 y=20/x
- further examples: find y when x=30 y=20/30=0.6 find x when y=25 25=20/x x=20/25=0.8

- example y=5 when x=4 5=m/4 5x4=m=20 y=20/x
- for surface areas you add the area of each surface altogether,

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