Chapter 2 Math Notes

7/31/2019 Chapter 2 Math Notes

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Chapter 2 maths notes

Percentage as fraction

When writing a percentage as a fraction form multiply denominator by 100.When writing a percentage which is a decimal you multiply numerator and

denominator by an appropriate multiple of 10

Percentage as Decimal

When writing a percentage as a decimal divide the percentage by 100-

move decimal point 2 places to the left

Fractions to percentage

There are two ways to turn fractions to percentages you can either turn the

denominator into a denominator of 100 or you can multiply the fraction by

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Decimals to percentage

When turning decimals to percentages you multiply the decimal by 100

Percentage of an amount using fractions

To find a percentage of an amount (for example 20% of $35):

1. Write the percentage as a fraction with a denominator of 100.

2. Change the of to a .

3. Write the amount over one if it is not already a fraction.

4. Cancel.

5. Multiply the numerators and multiply the denominators.

6. Divide the numerator by the denominator.

Percentage of an amount using decimals

To find percentages using decimals, follow these steps.


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1. Write the percentage as a number out of 100, and then change it to a

decimal by

Moving the position of the decimal point two places to the left and filling in

any

Gaps with zeros. For example 64.5% would be 0.645 as a decimal. (See

worked

Example 5 on page 38.)

2. Change the of to a .

3. Multiply the decimal by the amount.

One amount as a percentage of another

To express one amount as a percentage of another, follow these steps.

1. Write the amount as a fraction of the total:

2. Multiply by and write the % sign.

3. Cancel.

4. Multiply numerators and multiply denominators.

5. Simplify your answer if possible.

Remember if conversions are not the same make them the same, try not to

deal with decimals when doing conversions, convert the bigger one.

Increasing and Decreasing by a certain

percentageWhat you do is when increasing by a certain percentage you add 100% to

the percentage and then do percentage of the amount using either

fractions or decimals and then get the final answer.

When decreasing you take away 100% from the percentage and then do the

percentage of the amount and then get the final answer

Applications of Percentages


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Different Examples of applications of percentages include Sales,

Commission, Profit and loss, also Simple interest which is the same thing.

To find sales prices

Find key notes which indicate what you must do whether you must reduce,

increase etc. Then you follow the method needed to find the answer.

To find Commission

To find commission you put the percentage over 100 and multiply by the

other number and then divide to get the answer. You use the finding

percentages of an amount using fractions method.

Find Simple Interest (SI) - Use PRN

Principal amount

Rate of interest

No. of time period (years for now)

To find how much must be repaid you add the interest onto the actual loan

or price.

Comments

When you get your answer if it is a decimal just make sure you dont write

in the extra 0s

Always check answer along with question

Recheck answers, re-do questions

Remember to simplify

Listen to the question.

Summary

1. Per cent means out of one hundred

2. To change a percentage to a fraction put the percentage

over 100 and divide


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3. To change a percentage to a decimal , put the percentage

over 100 and change the fraction to a decimal by

changing the position of the decimal point two places to

the left

4. To change a fraction or decimal to a percentage multiply

by 100.

5. To find a percentage of an amount, put the percentage

over 100 change the of to an x and multiply by the second

amount.

6. Discount is one example of how percentages are used in

everyday life.

7. To find 10% of an amount, move the position of the

decimal point one place to the left.

8. One way to find 5% is to first find 10% and then halve it

9. To multiply a decimal by 100, move the position of the

decimal point two places to the right

10. When simplifying a fraction , divide the numeratorand the denominator by the same amount

11. The decimal point is at the end of the whole number

12. When multiplying decimals, the number of decimal

places in the answer is the denominator as the number of

decimal places in the question.

Profit= extra money received from the price you paid for the

object you sold.

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Chapter 2 Math Notes