**This is the Study List for the Maths Test on Thursday 16th November**

**Topic 1: Continuous Data**

- To be able to
**distinguish**between**discrete and continuous data** - To be able to fill in a
**frequency table for continuous data** - To be able to draw a
**simple histogram (bar chart for cts data)**from a frequency table - To be able to draw a
**frequency polygon**from a histogram or frequency table

**Topic 2: Probability**

- To be able to
**draw a possibility space diagram**to show all of the combined possibilities of two events happening together - To be able to
**find probabilities**from a possibility space diagram - To be able to distinguish between
**mutually exclusive, dependent and independent events** - To be able to
**draw a probability tree diagram**to show all of the combined possibilities of two independent events - To be able to
**find probabilities**from a probability tree diagram

Revision Sheet: Revision HW Worksheet Probability

**Topic 3: Percentages**

- To be able to answer Percentage Increase/Decrease Situations
- To be able to
**find the new value**given the original value and percentage - To be able to
**find the original value**given the new value and percentage - To be able to
**find the percentage**given the new value and original value

- To be able to
- To be able to find the
**simple interest**(formula gives S.I.)- or final amount (A = S.I. + P)

- To be able to find the
**compound interest**(C.I. = A – P)- or final amount (formula gives final amount (A) )

- To be able to find the
**rate/time/principal**given the other values

*How to study?*

*Go over all of the PowerPoints posted on the blog each week to remember exactly what we did in class. Work any examples on the slides to assess yourself**Go over the Maths notes given.**Go over the Classwork/Homework given**Use the book for additional explanations & examples to work out**Find resources/games online*

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So I was studying for the percentages topic and with the mixed problems involving increase/decrease I saw that the multiplier depended on the situation.When does the multiplier turn to × and when does it turn into ÷?

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Hey Jake 🙂

Yes the multiplier depends on the situation. It depends on whether the situation is portraying a percentage increase or decrease. However, it doesn’t depend on whether you are finding the new value (when you x) or the original value (when you ÷) for finding both of these the multiplier is the same, it depends on whether the whole situation is talking about an increase or decrease.

Example 1.1:

A packet of crisps normally weighs 125g. The packet is increased in weight by 20%. What is the new weight of the packet of crisps?

The situation is talking about an INCREASE. A packet used to weigh an amount and the amount increased. So the multiplier is found by adding 20% to 100%.

Multiplier: 100 + 20 = 120% –> 1.2

The multiplier is 1.2

Here we need to find the NEW VALUE:

NEW VALUE = ORIGINAL VALUE x MULTIPLIER

NEW VALUE = 125 X 1.2

NEW VALUE = 150g

Now consider the same situation, asking you for the original value.

Example 1.2:

After a 20% increase, a packet of crisps weighs 150g. How much did it weigh before?

The situation, is talking about an increase. The multiplier is therefore 100 + 20 = 120% –> 1.2

This time I was given the New Value and need to find the Original Value:

ORIGINAL VALUE = NEW VALUE ÷ MULTIPLIER

ORIGINAL VALUE = 150 ÷ 1.2

ORIGINAL VALUE = 125g

Whenever you are asked to find the New Value you MULTIPLY the original value by the multiplier.

Whenever you are asked to find the Original Value you DIVIDE the new value by the multiplier.

But the value of the multiplier depends on the situation, it doesn’t depend on what you are finding!

So Example 2.1:

A pair of trainers is at 15% off. The trainers were €60 before the sale. How much will they cost me now?

This situation is talking about a DECREASE. Trainers are on sale! So the multiplier is found by subtracting 15% from 100%.

Multiplier: 100 – 15 = 85% –> 0.85

Now, this question is asking me for the NEW VALUE.

NEW VALUE = ORIGINAL VALUE X MULTIPLIER

NEW VALUE = 60 X 0.85

NEW VALUE = €51

Example 2.2:

A pair of trainers is at 15% off. The new sale price is €51. How much did the trainers cost before the sale?

The situation is talking about a decrease. Therefore, the multiplier is 100 – 15 = 85% –> 0.85

This time I am asked to find the Original Value:

ORIGINAL VALUE = NEW VALUE ÷ MULTIPLIER

ORIGINAL VALUE = 51 ÷ 0.85

ORIGINAL VALUE = €60

Hope this answers your question. If you still have some questions, feel free to ask me next week 🙂

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