### ACT Math Topics

## Least Common Multiple (LCM)

To find the least common multiple of a set of numbers you have several methods to choose from.

- List out the multiples of each number and see which one is the least they have in common.
- Use the prime factors of each each number to determine the least common multiple mathematically.
- Use the built in functionality of the TI-84.

Watch this tutorial to learn how to solve LCM ACT Math problems. LCM Tutorial

**Example LCM Problem**

## Greatest Common Factor (GCF)

To find the greatest common factor of a set of numbers you have several methods to choose from.

- List out the factors of each number and see which one is the greatest they have in common.
- Use the prime factors of each each number to determine the greatest common factor mathematically.
- Use the built in functionality of the TI-84.

Watch this tutorial to learn how to solve GCF ACT Math problems. GCF Tutorial

**Example GCF Problem**

## Divisibility

In these types of problems you need to choose the correct number that gives a certain remainder when divided by a particular number.

Skills needed

- Eliminate answer choices that are divisible by the number.
- Do long division in order to get the remainder.
- Useful to know your times tables.

**Example Divisibility Problem**

## Absolute Value

When you see a numuber or expression with a set of vertical bars, that means find the absolute value. The absolute value of a number is how far it is from zero and it always positive. So, simply make what's inside the vertical bars positive.

**Example Absolute value Problem**