A **pattern rule** tells how to build a pattern. You may be able to state a pattern rule in more than one way.

The **core** of a pattern is the smallest part that repeats.

In a *repeating pattern*, the numbers change in the same way each time. The numbers can either be added or subtracted, as long as it is **the same amount each time**.

Repeating patterns may include operations other than addition. See the examples below.

A **growing pattern** is a pattern in which the numbers increase, and the amount added changes each time in a predictable way.

For example,120, 121, 123, 126, 130, 135, 141, ...

The pattern rule is start at 120. Add 1. The amount you add increases by 1 each time.

Another example would be 870, 880, 889, 897, 904, 910...

The pattern rule is start at 870. Add 10. The amount you add decreases by 1 each time.

Note: In some cases a number pattern can be classified as both a repeating pattern, and a growing pattern.

The pattern (4, 8, 16, 32, 64,...) can be identified as a repeating pattern because each time the previous number is multiplied by 2. However, you can also see that you can add to each number, and because you would be adding by different amounts each time, the pattern can also be identified as growing.

A **shrinking pattern** is a pattern in which the numbers decrease, and the amount subtracted changes each time in a predictable way.

For example, 81, 72, 64, 57, 51, 46...

The pattern rule is start at 81. Subtract 9. The amount you subtract decreases by 1 each time.

Another example would be 537, 535, 531, 523, 507, 475...

The pattern rule is start at 537. Subtract 2. The amount you subtract doubles each time.

Core

The *core* of a pattern is the smallest part that repeats.