# Edexel Maths Unit 3

All of the stuff for Edexel Maths Unit 3

- Created by: Charlotte
- Created on: 02-06-12 11:29

## Maths. Why Do I Have to Do Maths?

## All i did in lessons was mess about with calculato

## So,

## Heregoes...Standard Index Form

Standard Index Form can be used to write very small or very big numbers.

A × 10 ^{n}

- "A" is always between 1 and 10
- "N" is the number of decimal places moved
- If its a small nimber, the power is a minus, its stays normal if it is a big number

eg.

- 920 000 = 9.2 X 10
^{5} - 0.007 03 = 7.03 X 10
^{-3 }

## Proportion (Direct)

Direct Proportion: y = kx

Both increase together

## Proportion (Inverse)

Inverse Proportion: y = k/x

One increases and the other decreases

## Proportion (Inverse Square Variation)

You can have all sorts of relationships between x and y, like y = kx2 or y = kx3 etc. The most important type is y = kx2 and is called **inverse square variation**.

lol. a square watermelon.

## Percentage (Calculate the Original amount of Perce

Most people get these wrong. Dont be one of those people or you'll fail the exam.

EXAMPLE: A hampster increases in value by 20% to £72 000. Find out what it was worth before the rise.

METHOD:

- £72 000 = 120%
- Divide by 120 - £600 = 1%
- Times by 100 - £60 000 = 100%, so the original price was £60 000

## Repeated Proportional Change Problems

EXAMPLE: Charlotte buys a massive jar of paint for £800. The Paint loses a quarter of its value each year. Find the Value of the paint after 3 years.

- Value after 1 year is: £800 X 0.75 = £600
- Value after 2 years is: £600 X 0.75 = £450
- Value after 3 years is: £450 X 0.75 =
**£337.50**

## Just had a nice bowl of Tomato Soup for Lunch...

## I cant actuall do any more math. I cant be that cr

## So im going to have a lovely tea break.

## And then do something else like watch LOST...

## Bounds

**Maximum and Minimum Values for Calculations** - When a calculation is done using **rounded off values**, there will be some discrepency between the **calculated value** and the **Acual value.**

**Upper and Lower Bounds of a Measurement** - THE SIMPLE RULE: The real value can be as much as **half the rounded unit** abouve and below the rounded off value.

## Example of Bounds

A garden is measured as being **5.3 m X 4.2 m** to the nearest **10 cm**. This gives an area of **22.26m2**, but this is not the actual floor area because the real values could be anything from **5.25 and 5.35** and **4.15 and 4.25.**

- The maximum possible garden area :
**5.35 X 4.25 = 22.7375 m2** - The minimum possible garden area:
**5.25 X 4.15 = 21.7875 m2**

## The Four Main Facts of Reciprocals

- The reciprocal of a number is 'one over' the number
**eg. the reciprocal of 5 is 1/5** - You can find the reciprocal of a fraction by turing it
*upside down***eg. the reciprocal of 3/8 = 8/3** - A nuber multipled by its reciprocal gives 1.
**eg. 6/7 X 7/6 = 1** - 0 has no reciprocal because you cant divide anything by 0

## I really want a pot noodle right now...

## Solving Equations

- Get rid of any square root signs by
**squaring both sides** - Get every thing off of the bottom by
**cross multiplying**up to**every other term** **Multiply out**brackets- Collect all
**subject terms**on one side of the = and all**non-subject terms**on the other. Remember to**reverse the + / -**sign of any term that crosses the = **Combine together like terms**on each side of the equation, and reduce it to the form ax = b, where A and B are just numbers (or bunches of letters)- Slide a underneath b to give x = b/a, divide and thats the answer

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