What you need to know for the SAT from a basic level? Well, below is a pretty good answer. Though the information below won’t pertain to every question, they are important fundamentals/terminology that you should know walking into the test.

## Prime numbers

A prime number is a number divisible by itself AND 1.

1 is not a prime number because 1 IS itself. Don’t worry if your head can’t wrap around that logic. Just remember, 1 is not a prime number.

2 is the lowest prime number and the only even prime. It is good to be familiar with the prime numbers up to 30, though you don’t have to memorize them.

## Multiples, divisors, and factors

A multiple of n results if you multiply n by any positive integer. For instance,

3 x 1 = 3,

3 x 2 = 6,

3 x 3 = 9

3 x 4 = 12

These are all multiples of 3.

A factor is a smaller part of a larger number. Mathematically, factors are the numbers that form a larger number when you multiply them. In the example using 24 below, ‘2’ and ‘12’ are factors of ‘24’ because when you multiply them together you get 24.

24: 1, 2, 3, 4, 6, 8, 12, and 24 are factors of 24 (note that ‘24’ is both a factor and a multiple of ‘24’. In math terms, for every integer n, n is both a factor and a multiple of itself.

The prime factors of a number are the factors broken down to prime numbers. To find the prime factors, choose two factors of a number, say ‘3’ and ‘8’ (3 x 8 =24). Keep figuring out the factors for the number(s) that remain that are not primes. ‘3’ is a prime; however, ‘8’ is not. It can be broken into 2 x 2 x 2. Therefore, the prime factors of ‘24’ are 2, 2, 2, and 3.

## Evens and odds

Odd + odd = even

Odd + even = odd

Even + even = even

Don’t feel you have to memorize these. You can just plug in any odd or even number to derive the relationships.

1% = 1/100 = .01

10% = 1/10 = .10

50% = ½ = .5

## Adding fractions and multiplying factions

A quick trick for adding two fractions in which the numerator for both is ‘1’:

The numerator equals the sum of the numbers in the denominator; the denominator is the product of these two numbers. In the fraction below, all I have to do is add 2 and 3 for the top (giving me 5) an multiply 2 x 3 for the bottom (giving me 6).

½ + 1/3 = 5/6

Some other examples:

¼ + 1/6 = 10/24 = 5/12

1/5 + 1/7 = 12/35

1/3 + ¼ = 7/12

For multiplying fractions, just multiply across the numerator and across the denominator.

2/3 x 4/5 = 6/15 = 2/5

3/10 x 5/2 = 15/20 = ¾

½ x ¼ x ½ = 1/16