Pre-Algebra Notes

 
Concepts
- Digit
- Whole number place values
- Scientific Notation
- Exponential Notations
- Decimal place values
- Factors
- Reciprocal
- GCF
- LCM
- Square
- Square root
 
Whole Numbers
-
Place Values
- Expanded Form of Whole Numbers
- Rounding
- Comparison
Decimals
-
Place Values
- Comparison
- Terminating
- Non-Terminating
- Conversion Decimal to Fraction
 
Fractions
-
Comparison
- Denominator
- Numerator
- Conversion Fraction to Decimal
- Conversion of Mixed Number to
   Improper Fraction.
- Converting Improper Fraction to a Mixed Number.
- Adding Fractions with Like
   Denominators
- Adding Fractions with Unlike Denominators
- Subtracting Fractions with Like
   Denominators
- Subtracting Fractions with unlike Denominators
- Multiplying Fractions
- Multiplying Fractions and Whole
   Numbers
- Multiplying Mixed Numbers.
- Dividing Fractions
- Dividing Fractions by Whole Numbers
- Dividing Mixed Numbers
Integer
-
Addition
- Subtraction
- Multiplication
- Comparison
- Graphing
- Double Negatives
 
 
  Digit

A number (0 - 9) used to make up larger numbers.    

Example: The digits 4, 6, and 8 are used to write the numbers:
468
684
846
......
  Comparison Symbols:
<    is less than
>    is greater than

3 < 5

7 > 3

  Place values of a whole number

 

Expanded Form of Whole Numbers

Determine the multiples of 10 that can be added together to get the number you started with.

Write them as an addition problem.

 

1463   = 1000 + 400 + 60 + 3

64201 = 60000 + 4000 +200 + 1

 

Rounding Whole Numbers:

Identify what increments are to be used (count by 10s, 100s, 1000s, ....)

Surround the original number by counting using the increment (10, 100, 1000, etc.)

Figure out which of the incremental numbers is closest to your original number and choose that number as the answer.

If the original number is half way between two numbers, chose the larger number as the number that is closest.

Rounding 749 to the nearest 10s.
- Think of 740, 750, 780
- 749 is between
    740 and 750.
- 749 is closest
   to 750.
- The answer is 750.
Rounding 45 to the nearest 10s. 
- Think of 30, 40, 50.
- 45 is half way
   between 40 and 50.
- Assume 45 is closest
   to 50.
- The answer is 50.
 

Comparing Whole Numbers

Using a comparison symbol with whole numbers:

When writing the symbol, always point to the smaller number, wherever it is ....

When reading the symbol, always say whether the first number is greater or less than the second.    

 

975 < 983

2478 > 195

8 < 19

34 > 19

  Scientific Notation

    A x 10N

 

7 x 103

  Place values of decimal digits

  Factors

Things that can be multiplied together to give a specified number.

 

3  x  6 = 18 

so, 

   3 and 6 are FACTORS of 18.

  Greatest Common Factor
Given two or more whole numbers, the largest factor that can be found in all whole numbers.
8:    2,  4,  8

36:  2,  3,  4,  6,  9,  12

GCF:   4

  Least Common Multiple
Given two or more whole numbers, the smallest number that is a multiple of the numbers.
6:    6,   12,  18, 24

8:    8,   16,   24

LCM:  24

     
  Base
The thing that is being repeated in the multiplication.
Given:                  

73

 7      is the BASE

  Exponent
The number of times that a thing is multiplied times itself.
Given:                   

y5

 5   is the exponent.

  Exponential Notation
Short hand notation for the repeated multiplication of a number(or variable) times itself.
12 x 5 y4
  The square of a number "n"
The number that you get if you multiply the number  "n" x "n".
 square of n =  n2

square of 7 = 49

  The square root of a number "n"
The number "a" such that 

a x a = "n"

square root of  n =

square root of  49 = 7    

 

  Fact:
a0 = 1
70 = 1
  Denominator

Number on the bottom of a fraction.

  Numerator

Number on the top of a fraction.

 

  Addition of Fractions with like denominators
Add the top numbers.
Copy the bottom number to answer.
Reduce/Simplify the answer.
  Subtraction of Fractions with like denominators
Subtract the top numbers.
Copy the bottom number to the answer.
Reduce/Simplify the answer.
  Converting a Fraction to decimal
Divide bottom  number into top number.
Add a decimal point.
Copy the decimal point straight up.
Add a zero after the decimal point.
Divide.
Reduce/Simplify the answer.
  Converting a Decimal to a Fraction
Determine the place value of the last decimal digit.
Use the place value of the last decimal position to rewrite the decimal as a fraction
Reduce/Simplify the fraction.
  Terminating Decimals
Decimal that has a definitive end.
0.23

0.532

  Non-Terminating Decimal
Decimal that does not have a definitive end.
 
  Comparing Fractions
Use a number line.
Fractions to the left are smaller than fractions to the right.
  Comparing Fractions
Cross multiply from the bottom to the top numbers. (Place the result over the top of the fraction).
Point the comparison symbol to the fraction under the smaller number.
  Comparing Fractions
Adjust fractions to have common denominators
Compare numerators.
Point the comparison symbol to the fraction with the smaller numerator on the fractions with common denominator.
  Multiplying a Fraction with a Fraction
Multiply top numbers together.
Multiply bottom numbers together.
Reduce/Simplify the answer.
  Multiplying a Fraction with a Whole Number
Place a ONE under the whole number.
Multiply the top numbers together.
Multiply the bottom numbers together.
Reduce/Simplify the answer.
  Multiplying a Fraction with a Mixed Number
Convert the mixed number to an improper fraction.
Multiply the top numbers together.
Multiply the bottom numbers together.
Reduce/Simplify the answer.
  Multiplying a Mixed Number with a Mixed Number
Convert the mixed numbers to improper fractions.
Multiply the top numbers together.
Multiply the bottom numbers together.
Reduce/Simplify the answer.
  Reciprocal
A fraction turned upside down.

 

  Dividing Fractions
Rewrite the problem as a multiplication problem
Change the division sign to multiply sign
Change the fraction on the RIGHT to it's reciprocal
Bring down the fraction on the LEFT.
Multiply the fractions.
Reduce/Simplify the answer.
     
  Convert Mixed Number to an Improper Fraction
Multiply bottom number time the integer, add the top number.
Copy the bottom number to the answer.
  Convert Improper Fraction to Mixed Number
Divide bottom number into the top number.
Turn remainder into a fraction.
 
     
 
Integer Addition

Case 1:   Both terms have the same sign ...

Add the absolute values of the terms.
Place the sign of the added terms in front of the answer.

Case 2:  Both terms have different signs ...

Subtract the numbers.
Place the sign of the larger number in front 
of the answer.
-5 + (-6) = -11
7 + 6 = 13

 

 

-5 + 6  = 1
9 + (-11) = -2
  Integer Subtraction
Convert the problem to an addition problem
Do Integer Addition.
-6 - 11 
-6 + (-11)
 
5 - 8
5 + (-8)
 
8 - (-7)
8 + 15
  Integer Multiplication

Case 1:  Both terms have the same sign

Multiply the numbers.
Make answer positive. 

Case 2: Both have have different signs

Multiply the numbers.
Make the answer negative. 
 

 

(-5)(-6) = 30
8(5) = 40

 

-9(4) = -36
8(-7) = -56
  Double Negatives

-(-a)   = a

 

-(-5)   =  5

-(-(-9)) = -9

  Integer Comparison
Graph numbers on the number line.
Numbers to the left are smaller.

 

-5 < 8

-8 < -3

-12 > - 30

8 > -2

     
     
     
  Ratio
Comparison of two numbers.
3 to 1

3 : 1

3 / 1

  Proportions
 
 
     
  Ratio & Proportion  
  Percent
Ratio of a number to 100.
7%                 7 : 100

15%            15 : 100

125%        125 : 100

  Percent to Decimal
Shift decimal point two places to the left.
Remove the percent sign.

 

  (If no decimal point is specified in the percent, the decimal point is between the last digit and the % sign.)

  7%      =       .07

23%       =       .23

123%     =     1.23

211/3 % =    .211/3  

  Percent to Fractions
Convert percent to a decimal.
Convert decimal to a fraction.
Reduce the fraction.
7% = .07 = 7/100 

56% = .56 = 56/100 = 14/25

  Decimal to Percent
Shift decimal point two places to the right.  (Add extra zeros if necessary.)
Add a percent sign.
.2         =    20%

.03       =    3 %

.27       =    27%

.125     =    12.5%

  Fraction to Percent
Convert the fraction to a decimal.
Convert the decimal to a percent.
1/5     =>   5) 1    

0.2  =>  20% 

     
  Percent 'of'
Convert 'of' to a times sign.
Convert the percent to a decimal.
Copy the other number.
Multiply the decimal times the other number.
15% of $200
.15 x $200
    $30
  Percent 'off'
Convert 'off' to a times sign.
Convert the percent to a decimal.
Copy the other number.
Multiply the decimal times the other number to get the DISCOUNT.
Subtract the DISCOUNT from the original number to get the SALES PRICE.
 
20% off $3400
.20 x $3400
$680
$3400 - $680
$2720
  What Percent?
Convert 'is' to equal sign(=).
Convert the word 'What' to W.
Convert the word 'of' to a times sign
Divide the solitary number by the number closest to the W.
Convert the result to a percent.

What % of 300 is 15 ?

W x 300 = 15

               0.05

    300 ) 15.00

5%

     
     
  Statistical Display: Bar Graph  
  Statistical Display: Pie Graph  
  Statistical Display: Line Graph  
  Statistical Display: Histograph  
  Statistical Display: Venn Diagram  
  Statistical Display: Box & Whisker Plot
List the data in order from least to greatest.
Find the median.
Find the lower quartile ... the median of the lower half of the data (lowest number to the median).
Find the upper quartile ... the median of the upper half of the data (median to highest number).
Draw a number line ...
Mark the least and greatest values
Mark the lower and upper quartiles
Mark the median.
Draw a box using the lower and upper quartile marks as the bounds for the box.
Draw a whisker from the least number to the lower side of the box.
Draw a whisker from the greatest number to the upper side of the box.
Given the numbers:

12, 13, 14, 15, 16, 18, 19, 22, 24, 26, 28

The least is 12, the greatest data is 28
The median is 18,
The lower quartile is  14.
The Upper quartile is 24.
  Statistical Display: Stem & Leaf Plot  
  Statistical Display: Frequency Table

Table used to organize and display the frequency of individual numbers in a list of numbers.

Given ages (numbers): 
12, 13,13,15,15,16,16,16,
17,17,17,17,17,17,18,18,18
 
Age Count
12
13
14
15
16
17
18
1
2
 
2
3
6
3
(In this frequency table
the mode is 17 ... see the
explanation of mode.)
     
  Statistical Analysis: Data Range

The difference between the greatest number and the least number in the data.

Given student scores:

79, 80, 91, 68,74

The range is:

91 - 68 =  23

  Statistical Analysis: Quartiles
Lower Quartile
The median between the lowest value of data and the median of full data set.
Upper Quartile
The median between the greatest value of data and the median of the full data set.
 

 

 

 

 

  Interquartile range

The difference between the lower quartile and the upper quartile.

 
  Statistical Analysis: Mean
Add all numbers in the list of  numbers.
Divide by the count of numbers in the list.
Given class scores: 

79, 82, 71,84,80, 77

The mean(average) is:

 79+82+71+84+80+77
                    6
               78.83%
  Statistical Analysis: Median
For an odd number of data, the median is the middle number when the data is arranged in order.
For an even number of data, find the mean of the two middle numbers. 

 

 
  Statistical Analysis: Mode

The number that occurs most frequently in the data.  

 

It is possible for more than one number to be the mode if the count is the same for two or more items that happen the most.

Given ages (numbers): 
   12, 13,13,15,15,16,16,16,
   17,17,17,17,18,18,18,18
 
Age Count
12
13
14
15
16
17
18
1
2
 
2
3
4
4

The mode = 17 & 18

     
  Probability: Population

The totality of all potential measurements or observations under consideration in a given problem situation.

 
  Probability: Sample

A collection of measurements or observations taken from a given population.

 
  Probability: Experiment

Some process or operation that leads to a well-defined outcome.

 

Flipping a coin.

 

Counting left handed students in a room.
  Probability: Outcome

The results of a single trial of an experiment..

 

 

Finding flipping a coin comes up with a head.

 

Counting 2 left handed students in a classroom.
  Probability: Odds

Ratio of the number of positive outcomes to negative outcomes.

Container contains 5 red balls and 8 blue balls. The odds of drawing a red ball from the container are 5 to 8. 
  Probability Event: Simple

The outcome of a single trial in a particular experiment.

The result of tossing a coin once and having the coin land either heads or tails ... one simple event.
  Probability Event: Compound

A set of simple random events or a subset of the sample space.

 

 
  Probability Event: Independent

 

The events resulting from drawing two cards from a deck, returning the card to the deck each time.   Result is two independent events.
  Probability Event: Dependent

 

The events resulting from drawing two cards from a deck without returning the cards to the deck.   The result of the second draw is limited by the result of the first draw.
  Probability Event: Mutually Exclusive

 

 
     
  Meaning of factorial:

Multiplication of a whole number by every number less than it..

     n! = n(n-1)(n-2) ....(1)

     with special case that ....   0! = 1

 

   3! = (3)(2)(1)  = 6

   6! = (6)(5)(4)(3)(2)(1) = 720

   0! = 1

  Meaning of Multiplication:
Shortcut to adding.
Shortcut to counting.

 

 

                   
                   
                   
 
Count the cells, you find ...
30 cells.
Count columns and rows ... we find ...
3 rows, 10 columns. 
Add the number of cells found in each column ... we find ...
     10 + 10 + 10 = 30 cells.
 
Multiply the number of rows times the cells in a column ... we find ...
3 x 10 = 30 cells.
  If a number (n) of acts are carried out, each act can be performed in the same number of ways (k), then the total number of possible outcomes for n acts is:

    (k)(k) ... (k), or kn

How many cookies ?
  4 cells x 4 cookies = 8 cookies.
 
How many chocolate chips?
  4 cells x 4 cookies x 4 chips =
                                  64 chips.
 
  If there are n acts which can be performed in k1, k2, ... kn ways, respectively, then the total number of different possible outcomes for the n acts in succession is :

(k1)(k2) ...(kn)

How many cookies? 
 3 cells x 4 cookies = 12 cookies.
 
How many chocolate chips ?
  3 cells x 4 cookies x 5 chips =
                                 60 chips.
 
     
  Statistical: Permutations

The way that objects can be arranged and grouped.  If there is a set of n objects, the number of ordered arrangements of objects will depend on r, the number of objects selected and arranged.

Permutations are referenced as ...

   Pnr= n(n-1)(n-2)(n-3) ... (n-r+1)

    or

         n!     

       (n - r)!

Given 5 cards, how many ways can we draw the 3 cards:

Pnr= 5(4)(3)

 

  Statistical Counting Combinations

The number of ways r objects can be selected from n objects without regard to order.

    n

(  r )

         n!     

       r!(n - r)!

Given 5 cards, how many combinations of 3 cards can we draw?

     

        =    5!     

       3!(5 - 3)!

    = 10 combinations

    How many outcomes can result from throwing 3 coins...
H H H
T H H
H T H
T T H
H H T
T H T
H T T
T T T

 8 different outcomes.

      2 possibility, 3 touses

 
    How many distinct combinations can you find for 3 coins ...
H H H All heads
T H H
H T H two heads
H H T
T T H
T H T two tails
H T T
T T T All Tails

4 combinations.

n = number of objects .... 3