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Patterns and
Sequences in
General
Mathematics
Learning Objectives
Describe patterns by inspection, including
in art and nature
Determine the next term in various
patterns including Fibonacci sequence
Identify the rule governing a pattern and
illustrate attributes of arithmetic and
geometric sequences
Patterns in Art
and Nature
Discover how patterns appear all around us in nature and
art
What is a
Pattern?
A pattern is a repeated or predictable arrangement of
numbers, shapes, or objects. Patterns follow specific
rules that allow us to predict what comes next. They
can be visual (like shapes and colors) or numerical
(like number sequences).
Examples: 2, 4, 6, 8... or ...
▲ ● ▲ ● ▲ ●
Recognizing
Patterns by
Inspection
Look for repetition or regular changes in sequences
Notice increases or decreases in
numbers
Identify recurring shapes or colors. Example: 2, 4, 6,
8… (increasing by 2)
Determining the
Next Term in
Patterns
To find the next term, identify the rule
connecting each term. Look at the pattern: 3, 6,
12, 24, ? Each term is double the previous term
(×2). Following this rule, the next term is 24 × 2 =
48!
Try it yourself: What comes next in 5, 10, 15, 20,
?
The Fibonacci
Sequence
The famous Fibonacci sequence appears in many natural
forms
Understanding
the Fibonacci
Rule
The Fibonacci sequence follows a simple but
powerful rule: each term is the sum of the
two previous terms. Starting with 0 and 1,
we get:
0, 1, 1, 2, 3, 5, 8, 13, 21, 34...
Interactive Challenge: What is the 10th Fibonacci
number?
Identifying Pattern
Rules
Addition or subtraction (arithmetic patterns)
Multiplication or division (geometric
patterns)
Alternating, repeating, or Fibonacci (recursive)
sequences
Example: Rule for 2, 4, 8, 16 is "multiply by 2"
Arithmetic
Sequences:
Definition &
Attributes
An arithmetic sequence is a sequence where each
term is found by adding a constant value (called the
common difference) to the previous term. Key
attributes include the first term (a₁) and common
difference (d).
Example: 3, 7, 11, 15, … where d = 4
Attributes of
Arithmetic Sequences
Illustrated
General term formula: aₙ = a₁ + (n - 1)d
Constant difference between consecutive
terms
Linear growth or decline pattern. Example: For 3, 7, 11, 15...
find the 10th term: a₁₀ = 3 + (10-1)×4 = 39
Classifications of
Sequence
FINITE SEQUENCE
A finite sequence has a specific
number of terms – it has a
beginning and an end.
Example: 2, 4, 6, 8, 10
(This sequence has 5 terms – it ends at 10)
Classifications of
Sequence
INFINITE SEQUENCE
An infinite sequence has no end- it goes on
forever. It keeps following the same rule
endlessly.
You can describe the rule, but you can’t list all
the terms.
Example: 1, 2, 4, 8, 16, …
(This sequence keeps doubling and never
stops)
Classifications of
Sequence
“…”
In mathematical notation, an
infinite sequence often includes
ellipsis “…” to show it continues.
Problem: Find the 20th term of
5, 8, 11, 14...
Step 1: Identify a₁ = 5, d = 3
Step 2: Apply formula a₂₀ = 5 + (20-
1)×3 = 62
Step 12:
Arithmetic
Sequence
Problem
Geometric
Sequences –
Definition and
Attributes
A geometric sequence is a sequence where
each term is found by multiplying the
previous term by a constant ratio. Key
attributes include the common ratio (r) and
the first term (a₁).
Example: 2, 6, 18, 54, … (r = 3)
Attributes of
Geometric
Sequences
Illustrated
General term formula: aₙ = a₁ × r(n-1)
Constant ratio between consecutive terms
Exponential growth (r > 1) or decay (0 < r < 1)
Example: For 2, 6, 18, 54... find the 5th term: a₅ = 2 × 3⁴ =
162
Find the 8th term: 3, 6, 12, 24, ...
a₁ = 3, r = 2 a₈ = 3 × 2⁷ = 384
→
Step 15:
Geometric
Sequence
Problem
Comparing Arithmetic
and Geometric
Sequences
Arithmetic: Add constant difference →
Linear growth (e.g., 2, 5, 8, 11...)
Geometric: Multiply constant ratio →
Exponential growth (e.g., 2, 6, 18, 54...)
Key difference: Arithmetic grows
steadily, Geometric grows rapidly!
Solving Real-
World Problems
with Sequences
Arithmetic Example: You save $50 more
each month. Starting with $100, your
savings grow: $100, $150, $200, $250... Use
aₙ = a₁ + (n-1)d to find any month's total!
Geometric Example: Bacteria double every hour: 1, 2, 4, 8,
16...
Key Takeaways
Patterns appear everywhere in nature and art
Fibonacci is a special recursive
pattern
Arithmetic adds constant; geometric multiplies
ratio
ARITHMETIC SEQUENCE |
EXAMPLES
Example 1
The sequence is:
7, 12, 17, 22, ...
Find the 20th term (a20)
Given:
a₁ = 7; n = 20
d = a2 – a1
d = 12 – 7
d = 5
Formula: aₙ = a1 + (n - 1)d
Solution:
a20 = a1 + (n - 1)d
a20 = 7 + (20– 1) x 5
a20 = 7 + (19) x 5
a20 = 7 + 95
a20 = 102
ARITHMETIC SEQUENCE |
EXAMPLES
Example 2
Find the 30th term of the arithmetic
sequence: −15, −9, −3, 3, ...
Find: a30
Given:
a₁ = -15; n = 30
d = a2 – a1
d = -9 – -15
d = 6
Formula: aₙ = a1 + (n - 1)d
Solution:
a30 = a1 + (n - 1)d
a30 = -15 + (30– 1) x 6
a30 = -15 + (29) x 6
a30 = -15 + 174
a30 = 159
ARITHMETIC SEQUENCE |
EXAMPLES
Example 3
The second term of an arithmetic
sequence is 18, and the common
difference is −4.
Find the 100th
term (a100)
Given:
d = - 4; n = 35
a₁ = a2 – d
a₁ = 18 – (-4)
a₁ = 22
Formula: aₙ = a1 + (n - 1)d
Solution:
a100 = a1 + (n - 1)d
a100 = 22 + (100 – 1) x -4
a100 = 22 + (99) x -4
a100 = 22 - 396
a100 = -374
ARITHMETIC SEQUENCE |
EXAMPLES
Solution:
a18 = a1 + (n - 1)d
a18 = 500 + (18 – 1) x 150
a18 = 500 + (17) x 150
a18 = 500 + 2550
a18 = ₱3050
Word Problem 1 – Savings
Maria saves ₱500 during the first week. She decides to increase the amount she
saves by ₱150 every week. If this pattern continues, how much will Maria save
during the 18th
week?
Find the 18th
week savings (a18)
Given:
a₁ = ₱500 ; n = 18th
week
d = ₱150
Formula: aₙ = a1 + (n - 1)d
ARITHMETIC SEQUENCE |
EXAMPLES
Solution:
a24 = a1 + (n - 1)d
a24 = 25000 + (24 – 1) x 800
a24 = 25000 + (23) x 800
a24 = 25000 + 18400
a24 = ₱43400
Word Problem 2 – Salary Increase
A newly hired employee receives a monthly salary of ₱25,000 during the first
month. Every succeeding month, his salary increases by ₱800.
What will be his salary during the 24th month?
Find the 24th
month salary increase (a24)
Given:
a₁ = ₱25,000 ; n = 24th
week
d = ₱800
Formula: aₙ = a1 + (n - 1)d
GEOMETRIC SEQUENCE | EXAMPLES
Example 1
Find the 12th term of the sequence:
3, 6, 12, 24, ...
Find the 12th
term (a12)
Given:
a₁ = 3
r = a2 / a1
r = 6 / 3
r = 2
n = 12
Formula: aₙ = a₁ × r(n-1)
Solution:
a12 = a₁ × r (n-1)
a12 = 3 × 2 (12-1)
a12 = 3 × 2 (11)
a12 = 3 × 2048
a100 = 6144
GEOMETRIC SEQUENCE | EXAMPLES
Example 2
Determine the 15th term of the
sequence:
2, 8, 32, 128, ...
Find the 15th
term (a15)
Given:
a₁ = 2
r = a2 / a1
r = 8 / 2
r = 4
n = 15
Formula: aₙ = a₁ × r(n-1)
Solution:
a15 = a₁ × r (n-1)
a15 = 2 × 4 (15-1)
a15 = 2 × 4 (14)
a15 = 2 × 268,435,456
a15 = 536,870,912
GEOMETRIC SEQUENCE | EXAMPLES
Example 3
The third term of a geometric sequence is
96, and the common ratio is ½.
Find the 10th term.
Find the 10th
term (a10)
Given:
r =
n = 10; a3 = 96
a2 = a3 / r
a2 =96 / 0.5 = 192
a1 = 192 / 0.5 = 384
Formula: aₙ = a₁ × r(n-1)
Solution:
a10 = a₁ × r (n-1)
a10 = 384 × (10-1)
a10 = 384 × (9)
a10 = 384 ×
a10 = 0.75
GEOMETRIC SEQUENCE | EXAMPLES
Solution:
a8 = 10000 × 1.20 (8-1)
a8 = 10000 × 1.20 (7)
a8 = 10000 × 3.5832
a8 = ₱35,831.81
Word Problem 1 – Investment
Carlos invested ₱10,000 in a business that grows by 20% every year.
Assuming the investment grows according to a geometric sequence, what will be
its value at the 8th year?
Find the 8th
year investment value (a18)
Given:
a₁ = ₱10,000 ; n = 8th
year
r = 100%(principal amount) + 20%
r = 120% or 1.20
Formula: aₙ = a₁ × r(n-1)
GEOMETRIC SEQUENCE | EXAMPLES
Solution:
a9 = 200 × 2 (9-1)
a9 = 200 × 2 (8)
a9 = 200 × 256
a9 = 51,200 bacteria
Word Problem 2 – Bacteria Growth
A laboratory culture contains 200 bacteria. Every hour, the number of bacteria
doubles. How many bacteria are present after the 9th hour?
Find: No. of bacteria present after the
9th hour (a9)
Given:
a₁ = 200 bacteria ; n = 9th
hour
r = 2 (the no. of bacteria doubles
every hour
Formula: aₙ = a₁ × r(n-1)
ASSIGNMENT
1. A patient takes 80 mg of medicine on the first day. Because of
recovery, the dosage is reduced by half every day. What will
be the dosage on the 7th day?
2. A community plants 45 trees during the first month of a
reforestation project. Each month, they plant 12 more trees
than they did the previous month. If they continue this
pattern, how many trees will they plant during the 24th
month?