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Pattern and Function - Rules for Patterns

Grade 3IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

A Pattern is a set of numbers, shapes, or objects that follow a specific, predictable rule. For example, a visual pattern might look like a row of alternating colored blocks: Red, Blue, Red, Blue.

A Repeating Pattern has a 'core' or a unit that repeats over and over again. If you see a sequence like ,,,\triangle, \square, \triangle, \square, the repeating core is ,\triangle, \square.

A Growing Pattern is a sequence where each term increases by a specific amount or follows a rule that makes it larger. Imagine a staircase made of blocks where the first step has 11 block, the second has 22 blocks, and the third has 33 blocks; this is a growing pattern where we add 11 each time.

A Shrinking Pattern is a sequence where each term decreases. Visually, this looks like a stack of coins getting shorter, such as starting with 1010 coins, then 88, then 66. The rule here is to subtract 22 from the previous number.

The Rule is the mathematical instruction that tells us how to get from one number to the next in a sequence. If a sequence is 5,10,15,205, 10, 15, 20, the rule is +5+5.

A Number Sequence is a list of numbers arranged in a specific order according to a rule. For example, 2,4,6,8,102, 4, 6, 8, 10 is a sequence of even numbers.

An Input-Output Table (or Function Machine) shows how a rule is applied to a set of numbers. Imagine a machine where you drop in the number 33 (Input), the machine adds 44 (Rule), and out pops 77 (Output). This can be visualized as a two-column table where every number in the left column is changed the same way to get the number in the right column.

Predicting Patterns involves using the identified rule to find missing terms or future terms. If the rule is +10+10 and the last number you see is 4040, you can predict the next number will be 5050.

📐Formulae

Term+Rule=Next TermTerm + Rule = Next \space Term

Rule=Term2Term1Rule = Term_{2} - Term_{1} (for growing patterns)

Rule=Term1Term2Rule = Term_{1} - Term_{2} (for shrinking patterns)

Output=Input+nOutput = Input + n (where nn is a constant)

Output=InputnOutput = Input - n (where nn is a constant)

💡Examples

Problem 1:

Find the rule and the next two numbers in the sequence: 12,15,18,21,12, 15, 18, 21, \dots

Solution:

Step 1: Find the difference between the first and second term: 1512=315 - 12 = 3. Step 2: Check the difference between the second and third term: 1815=318 - 15 = 3. Step 3: Identify the rule as +3+3. Step 4: Add 33 to the last known term (2121) to get the next number: 21+3=2421 + 3 = 24. Step 5: Add 33 to 2424 to get the following number: 24+3=2724 + 3 = 27.

Explanation:

Since the numbers are increasing, we use subtraction between consecutive terms to find the addition rule. We then apply that rule to extend the pattern.

Problem 2:

Complete the Input-Output table for the rule: Subtract 55 (Input5Input - 5). If the Inputs are 15,20,2515, 20, 25, what are the Outputs?

Solution:

Step 1: Apply the rule to the first input: 155=1015 - 5 = 10. Step 2: Apply the rule to the second input: 205=1520 - 5 = 15. Step 3: Apply the rule to the third input: 255=2025 - 5 = 20. The Outputs are 10,15,2010, 15, 20.

Explanation:

An Input-Output table applies the same mathematical operation to every input value to generate the corresponding output value.