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FF.2 Complete number patterns

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What are number patterns?

Number patterns are sequences of numbers that follow a specific rule or set of rules. Identifying these rules helps us predict future numbers in the sequence.

Examples:
  • 2, 4, 6, 8, 10... (increasing by 2)
  • 45, 40, 35, 30, 25... (decreasing by 5)
  • 3, 9, 27, 81... (multiplying by 3)
Note

Patterns appear everywhere in mathematics. Recognizing them helps develop problem-solving skills and mathematical thinking.

Arithmetic patterns

Arithmetic patterns change by repeatedly adding or subtracting the same value. This constant change is called the common difference.

Examples:
  • 5, 8, 11, 14, 17... (+3 each time)
  • 100, 95, 90, 85, 80... (-5 each time)
  • 12, 14, 16, 18, 20... (+2 each time)
Note

To identify an arithmetic pattern, subtract any number from the number that follows it. If the difference is always the same, you've found an arithmetic pattern.

Geometric patterns

Geometric patterns change by repeatedly multiplying or dividing by the same value. This constant multiplier is called the common ratio.

Examples:
  • 2, 6, 18, 54... (×3 each time)
  • 256, 64, 16, 4... (÷4 each time)
  • 5, 10, 20, 40... (×2 each time)
Note

To identify a geometric pattern, divide any number by the number before it. If the quotient is always the same, you've found a geometric pattern.

Two step patterns

Two-step patterns follow two different operations that alternate or follow a specific order.

Examples:
  • 3, 6, 8, 11, 13... (+3, +2 repeating)
  • 50, 48, 44, 42, 38... (-2, -4 repeating)
  • 2, 4, 8, 10, 20... (+2, ×2 repeating)
Note

When analyzing patterns, look at the differences between several consecutive numbers to identify if multiple operations are being used.

Growing and shrinking patterns

Patterns can either grow (increase) or shrink (decrease) based on their rules. Some patterns may even grow at an increasing rate.

Examples:
  • Growing: 10, 20, 30, 40... (+10 each time)
  • Shrinking: 80, 76, 72, 68... (-4 each time)
  • Increasing growth: 2, 6, 18, 54... (×3 each time)
Note

Geometric patterns with multipliers greater than 1 grow faster than arithmetic patterns because they multiply rather than add.

Finding missing numbers in patterns

To find missing numbers in patterns, first identify the rule, then apply it to find the unknown values.

Examples:
  • Pattern: 7, 14, __, 28, 35 (Rule: +7, Missing: 21)
  • Pattern: 64, 32, __, 8, 4 (Rule: ÷2, Missing: 16)
  • Pattern: 5, __, 15, 20, __ (Rule: +5, Missing: 10 and 25)
Note

When multiple numbers are missing, check the pattern before and after each missing number to confirm the rule remains consistent.

Extending patterns

Extending patterns means continuing the sequence by applying the same rule to find additional numbers.

Examples:
  • Pattern: 4, 12, 36, 108... Next: 324 (×3)
  • Pattern: 25, 22, 19, 16... Next: 13, 10 (-3)
  • Pattern: 1, 4, 9, 16... Next: 25, 36 (squares: 1², 2², 3²...)
Note

Always verify your rule works for at least three consecutive numbers before extending the pattern.

Strategies for identifying pattern rules

Use these strategies to identify pattern rules: look at differences between numbers, check for multiplication or division relationships, and test your rule on multiple numbers in the sequence.

Strategy Examples:
  • Check differences: 11, 15, 19, 23 (differences are +4)
  • Check ratios: 5, 15, 45, 135 (each ×3)
  • Look for alternating rules: 2, 4, 5, 10, 11... (×2, +1 repeating)
Note

The most reliable method is to test your proposed rule on at least three different positions in the pattern to ensure it works consistently.