Basic
Rules to Remember

Adding Two Numbers with
the Same Sign

Add
the two numbers together and keep the sign

_{}

**Adding Two Numbers with
Different Signs**

Subtract the two
numbers and keep the sign of the larger number.

_{}

**Multiplying and Dividing Real Numbers**

The product or
quotient of two numbers with the __same sign__ is a __positive number__.

2(3) = 6 -2(-3)
= 6

The product or
quotient of two numbers with __different signs__ is a __negative number__.

2(-3) = -6 -6
/ 2 = -3

Do you have a series
of multiplication to do with a number of negative and positive signs? Well, count
the number of negative signs and if you get:

An even number, your answer will be positive.

An odd number, your answer will be negative.

**Zero as a Divisor or Dividend**

1.
Any number that
is divided by 0 is undefined.

2.
Zero divided by
any number is equal to 0.

**Combining Like Terms (applies to addition and subtraction)**

Remember that apples
(x) can only be combined with apples (x), oranges (y) with oranges (y). You
cannot combine apples with oranges.

2x + x + 2y + y = 3x + 3y

We can __multiply__
or __divide__ apples and oranges.

2x(3y) = 6xy _{}

**Percents and Decimals**

Always change a
percent to a decimal by dropping the percent symbol and moving the decimal two
places to the left before multiplying or dividing.

87.5% = .875

If you are given an
answer in decimal form and need to know what percent it is, move the decimal
two places to the right and add the percent symbol.

.658 = 65.8%