Ch 2 Revision

Page 1

Ch 2 Notes

Fraction and Decimals

Fraction ----> Decimal

= numerator ÷ denominator

Arranging in Ascending and Descending Order

Ascending = small to big

Descending = big to small

Converting a Recurring Decimal To a Fraction

1) Change expanded recurring decimal to recurring decimal with dot or line

2) Let recurring decimal equal x

3) Times both by 100

4) Step 1 - step 2

5) Solve for x

Eg. 0.15151515 ----> 0.15--

Let x = 0.1515...

100x = 15.15

100x = 15.15 - x = 0.15

= 99x = 15

x = 15/99

Converting Fractions, Percentages and Decimals

Fraction to percentage:

Change to decimal then times by 100

Fraction to decimal:

Numerator ÷ denominator

Percentage to fraction:

Percentage / 100

Percentage to decimal:

Percentage ÷ 100

Decimal to fraction:

Make denominator 100

Decimal to Percentage:

Times by 100

Simplifying Fractions

+, - or ×

Combine symbols

Make improper

Make 1 a fraction

÷

Make improper

Stay, switch, flip

Simplify

Writing One Amount as a Percentage of Another

Formula: amount needed/total amount × 100

* use same units

Finding a Percentage of an Amount

10% - move decimal point 1 left

1% - move decimal point 2 left

Eg. Find 15% of $280

15/100 × 280 or 10% = $28.0 + 5% = 28/2

Percentage Increase

Formula: % increase + 100 / 100 × item cost = total amount

* GST = 10%

Eg. If a $509 laptop has a 10% GST added to it, find the total cost of the laptop.

= 10+100 / 100 × 509

= $59.90

Percentage Decrease

Formula: discount / original price × 100