# SAT Math Number Properties That You Should Know

# SAT Math: Number Properties That You Should Know

Number properties is one of the biggest math topics tested on the SAT math section. Students are expected to be familiar with concepts such as what an integers is, what a rational number, odd/even rules, and more. These are very common math questions. So, here are the common rules that you should know:

**Rules of Divisibility**

An integer is divisible by:

- 2 if the integer is EVEN.
- 3 if the SUM of the integers’ digits is divisible by 3. For example 54 is divisible by 3 because the sum of its digits is 9, which is divisible by 3.
- 5 if the integer ends in 5 or 0.For example, 20 and 55 are divisible by 5.
- 6 if the integers is divisible by both 2 AND 3. For exmaple 24 is divisible by 6 because it’s divisible by 2 AND 3.

**ODD & EVEN**

- What do you do to get an even number?
- Multiply any number, n, by 2. For example, 3 x 2 = 6; 4 x 2 = 8
- So, 2n = Even

- Multiply any number, n, by 2. For example, 3 x 2 = 6; 4 x 2 = 8
- What do you do to get an odd number?
- Make sure you have an even number and just add or take away 1. For example 3 x 2 + 1 = 7 or 3 x 2 – 1 = 5; 4 x 2 – 1 = 7 or 4 x 2 + 1 = 9
- So, 2n+1 or 2n-1 = ODD

- Make sure you have an even number and just add or take away 1. For example 3 x 2 + 1 = 7 or 3 x 2 – 1 = 5; 4 x 2 – 1 = 7 or 4 x 2 + 1 = 9

- When you add an ODD number to an EVEN number, you get an ODD number. For example, 3 + 4 = 7 or 2 + 11 = 13
- When you subtract and ODD number by an EVEN number, you get an ODD number. For example, 7 – 2 = 5 or 16 – 7 = 9
- When you add or subtract an EVEN number with another EVEN number, you get an EVEN number. Try it!
- When you multiply and ODD number by an ODD number, you get an ODD number. For example, 5 x 5 = 25 or 11 x 13 = 143
- When you multiply an EVEN number by an EVEN number, you get an EVEN number. Try it! (it’s also divisible by 4)!
- When you multiply an ODD number by an EVEN number, you get an EVEN number. For example, 3 x 4 = 12 or 5 x 20 = 100

Next time, we’ll go over more of the important topics for the SAT math section.