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Pattern and Function - Number Patterns and Sequences

Grade 3IB

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

🔑Concepts

A number pattern is a sequence of numbers that follows a specific rule. For example, in the sequence 2,4,6,82, 4, 6, 8, the rule is to add 22 to the previous number. You can visualize this as a growing tower of blocks where each new tower is 22 blocks taller than the one before it.

Ascending patterns are sequences where the numbers get larger. This usually involves addition or multiplication. Think of this like climbing up a ladder where each rung is a fixed distance higher than the last, such as +5+5 or +10+10.

Descending patterns are sequences where the numbers get smaller. This usually involves subtraction or division. Imagine a countdown timer or a cooling thermometer where the value drops by a consistent amount like 3-3 at every step.

The 'Rule' is the secret formula that connects one number to the next. If you have an Input/Output table, the rule describes what happens to the 'Input' number to turn it into the 'Output' number. For example, if the rule is ×2\times 2, then an input of 55 results in an output of 1010.

Repeating patterns involve a sequence of numbers or shapes that repeat in the same order. For instance, the sequence 1,3,5,1,3,51, 3, 5, 1, 3, 5 has a core of 1,3,51, 3, 5 that repeats. You can visualize this as a pattern of colored beads on a string that follows a cycle.

Skip counting is a basic form of number patterns. Counting by 22s (2,4,6,82, 4, 6, 8), 55s (5,10,15,205, 10, 15, 20), or 1010s (10,20,30,4010, 20, 30, 40) helps in identifying the common difference in arithmetic sequences.

Missing terms are found by first identifying the rule between the known numbers and then applying it to the empty spaces. If a pattern is 25,30,_,4025, 30, \_, 40, we see the difference between 2525 and 3030 is +5+5, so we add 55 to 3030 to find the missing number 3535.

📐Formulae

Term1+Rule=Term2Term_{1} + Rule = Term_{2}

Term1Rule=Term2Term_{1} - Rule = Term_{2}

Input×Rule=OutputInput \times Rule = Output

Input+Rule=OutputInput + Rule = Output

💡Examples

Problem 1:

Identify the rule and find 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 two numbers: 1512=315 - 12 = 3. Step 2: Check if this works for the next pair: 1815=318 - 15 = 3. The rule is +3+3. Step 3: Add 33 to the last known number: 21+3=2421 + 3 = 24. Step 4: Add 33 to that result: 24+3=2724 + 3 = 27. The next two numbers are 2424 and 2727.

Explanation:

To solve a growing pattern, calculate the difference between consecutive terms to find the constant addition rule.

Problem 2:

An Input/Output machine uses the rule 'Subtract 77'. If the Inputs are 20,25,20, 25, and 3030, what are the corresponding Outputs?

Solution:

Step 1: Apply the rule to the first input: 207=1320 - 7 = 13. Step 2: Apply the rule to the second input: 257=1825 - 7 = 18. Step 3: Apply the rule to the third input: 307=2330 - 7 = 23. The outputs are 13,18,2313, 18, 23.

Explanation:

In a function machine, every input number is transformed by the same mathematical operation to produce an output.