Math 20

**Variables** -- letters used to represent numbers in algebra

**Factors** -- the numbers or variables that are multiplied in a multiplication
problem. i.e.: a x b=c a and b are factors of c

**Numerator** -- top number of a fraction

Denominator -- bottom number of a fraction

**Simplified (reduced to its lowest terms)** -- the numerator and denominator have no common
factors other than 1

**Real number system **– double R is symbol for real numbers

**Whole numbers** – 0, 1, 2, 3, 4, etc.

**Counting numbers (natural numbers**) – 1, 2, 3, etc.

**Integers** -- …, -3, -2, -1, 0, 1, 2, 3, …

**Rational numbers** – all numbers that can be expressed in a fraction
(ratio) 2/3 , ½, -3/7, 4/1, etc.

**Irrational numbers** – cannot be expressed any other way.

**Prime numbers** -- can only be divided by themselves and 1 -- 2, 3,
5, 7, 11, 13, etc

1 is not a prime number. It is a **unit**.

All other numbers are **composite numbers**

**To simplify a fraction:**

Find the largest number that will divide without a remainder both the numerator and denominator. This number is called the greatest common factor or GCF

Then divide both the numerator and denominator by the GCF

6/18 = 6 divided by 6 over 8 divided by 6 = 1/3

**To multiply a fraction:**

Multiply their numerators together

Then multiply their denominators together

7/13 x 5/12 = 7x5 over 13x12 = 35/156

**To avoid having to simplify the answer:**

Divide both a numerator and a denominator by a common factor

6/17 x 5/12 6 and 12 divide by 6

6 divides 1 time and 12 2 times

1/17 x 5/2 = 1 x 5 over 17 x 2 = 5/34

**To multiply a whole number by a fraction:**

Write the whole number with a denominator of 1 and then multiply

12 x 5/64

12/1 x 5/64 12 and 64 both divide by GCF of 4

12 divides 3 times and 64 divides 16 times

3/1 x 5/16 = 3 x 5 over 1 x 16 = 15/16

**To divide a fraction by another:**

Invert the divisor -- the second fraction

Multiply

3/5 divided by 5/6

3/5 x 6/5 = 3 x 6 over 5 x 5 = 18/25

**Evaluate an expression -- to obtain the
answer to the problem using the operations given**

Evaluate 3/8 divided by 9

3/8 divided by 9/1 = 3/8 x 1/9 9 is divisible by 3

1/8 x 1/3 - 1 x 1 over 8 x 3 = 1/24

**Fractions with the same (common)
denominator can be added or subtracted**

**To add (or subtract) fractions with the
same denominator:**

Add (or subtract) the numerators

Keep the common denominator

9/15 + 2/15 = 9 + 12 over 15 = 11/15

8/13 - 5/13 = 8 - 5 over 13 = 3/13

**The smallest number that is divisible by
2 or more dominators is the least common denominator or LCD**

**To add (or subtract) fractions with
unlike denominators:**

Rewrite fractions with the same (common) denominator -- multiply numerator and denominator with the same number

Add (or subtract)

1/2 + 1/5 10 is the LCD

1/2 = 1 x 5 over 2 x 5 = 5/10

5/10 + 2/10 = 5 + 2 over 10 = 7/10

3/4 - 2/3 12 is the LCD

3/4 = 3 x 3 over 4 x 3 = 9/12

2/3 = 2 x 4 over 3 x 4 = 8/12

9/12 - 8/12 = 9 - 8 over 12 = 1/12

**Mixed number consists of a whole number
followed by a fraction: **5 2/3 = 5 +
2/3

**To change a mixed number to a fraction
(an improper fraction)**

Multiply the denominator of the fraction by the whole number

Add the numerator to the product from step 1. This sum represents the numerator of the fraction you are seeking.

The denominator of the fraction you are seeking is the same as the denominator of the fraction in the mixed number

5 2/3 = 5 x 3 = 15

15 + 2 over 3 = 17/3

5 2/3 = 17/3

**To change a fraction greater than 1 to a
mixed number:**

Divide the numerator by the denominator

Note the quotient and remainder

Write the mixed number. The quotient found in step 1 is the whole number of the mixed number.

The denominator in the fraction of the mixed number will be the same as the denominator in the original fraction

17/3

17 divided by 3 = 5 (whole number) and a remainder of 2

17/3 = 5 2/3

**To add, subtract, divide, or multiply
mixed numbers they are often changed into improper fractions**

** **

**Cross divide to check answers:**

13/26 = 1/2

Take 13 x 2 and 26 x 1. Both should give the same answer of 26. That tells you the answer is correct

**Absolute value** – the bars make the number inside positive.

│2 │ = 2

│-2│ =2

**Negative symbol outside
of absolute stays with number**

-│-2│ = -2

**For < or > solve
the absolute first**

│-7│ < or > │-8│

│-7│ = 7 and │-8│ = 8

7 < 8

│-7│ < │-8│

-│-3│ < or > │2│

-│-3│ = -3 and │2│ = 2

-3 < 2

-│-3│ < │2│

**For decimals ignore the
negative sign, find the greater than and do the opposite.**

-1.83 < or > -1.82

1.83 > 1.82 = -1.83 < -1.82

**DSS** – if the signs of the numerals are different,
subtract and take the sign of the larger number

-3 + 5 = 5 – 3 = 2

5 is larger than 3 so the number is positive

-12 + 7 = 12 – 7 = 5 = -5

12 is larger than 7 so the answer is negative

**SSA** – if the signs of the numerals are the same, add and
keep the sign

-9 + -7 = 9 + 7 = 16 = -16

**Two negatives make a
positive**

-5 - -7

-5 + 7 = 7 – 5 = 2 (DSS)

**A negative and a positive
double sign becomes a negative**

3 + -7

3 -7 = 7 – 3 = 4 = -4 (DSS)

**Same rules apply for multiplication.
**

Mixed signs are negative. Same signs are positive

**Commutative property of
addition and multiplication** – states
that the order in which any two real numbers are added does not matter.

A + B = B + A

4 + 3 = 3 + 4

7 = 7

**Associative property of
addition and multiplication** – states
that in addition of three or more numbers, parenthesis may be placed around any
two adjacent numbers without changing the results.

(A+B) + C = A + (B+C)

(3+4) + 5 = 3 + (4+5)

7 + 5 = 3 + 9

12 = 12

**Distributive property of multiplication
over addition** – anything on the outside
multiplies by anything on the inside.

A(B+C) = AB + AC

Ex: A = 2, B = 3, C = 4

2(3+4) = (2x3) + (2x4)

2x7 = 6 + 8

14 = 14

Also

A(B-C) = AB – AC

Ex: A = 4, B = 3, C = 2

4(3 – 2) = (4x3) – (4x2)

4 x 1 = 12 – 8

4 = 4

**Order of operations** – what order the problem is done. Parentheses,
exponents, multiplication, division, addition, subtraction

P

E

MD

AS

Negative numbers to the odd power will always give a negative number

Negative numbers to an even power will always give a positive number