# Operations on Numbers

• Area of a Rectangle
Rectangles are of fundamental importance in the portion of statistics that involves the uniform distribution. Every rectangle has a base and a height and an area.
• Factorials and Combination Notation
When we need to compute probabilities, we often need to multiple descending numbers. For example, if there is a deck of 52 cards and we want to pick five of them without replacement, then there are 52 choices for the first pick, 51 choices for the second pick since one card has already been picked, 50 choices for the third, 49 choices for the fourth, and 48 for the fifth.
• Order of Operations
When we are given multiple arithmetic operations within a calculation, there is a, established order that we must do them in based on how the expression is written.  Understanding these rules is especially important when using a calculator, since calculators are programmed to strictly follow the order of operations.  This comes up in every topic in statistics, so knowing the order of operations is an essential skill for all successful statistics students to have.
• Order of Operations in Expressions and Formulas
We have already encountered the order of operations: Parentheses, Exponents, Multiplication and Division, Addition and Subtraction. In this sections we will give some additional examples where order of operations must be used properly to evaluate statistics.
• Perform Signed Number Arithmetic
Even though negative numbers seem not that common in the real world, they do come up often when doing comparisons.  For example, a common question is how much bigger is one number than another, which involves subtraction.  In statistics we don't know the means until we collect the data and do the calculations.  This often results in subtracting a larger number from a smaller number which yields a negative number.  We need to be able to perform arithmetic on both positive and negative numbers.
• Powers and Roots
It can be a challenge when we first try to use technology to raise a number to a power or take a square root of a number. In this section, we will go over some pointers on how to successfully take powers and roots of a number. We will also continue our practice with the order of operations, remembering that as long as there are no parentheses, exponents always come before all other operations. We will see that taking a power of a number comes up in probability.
• Using Summation Notation
When we have an expression with many numbers added to each other, there is a notation that makes the formulas easier to write down.