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Quizzes > High School Quizzes > Mathematics

Geometric Sequences Practice Quiz

Practice identifying geometric sequences in everyday problems

Difficulty: Moderate
Grade: Grade 8
Study OutcomesCheat Sheet
Colorful paper art promoting Geometric Sequence Showdown, a math trivia quiz for high school students.

Which of the following sequences is geometric?
4, 7, 10, 13
2, 5, 8, 11
1, 3, 7, 15
3, 6, 12, 24
A geometric sequence has a constant ratio between consecutive terms. In this case, 6/3 = 2, 12/6 = 2, and 24/12 = 2, confirming that the sequence is geometric.
What is the common ratio of the geometric sequence: 5, 15, 45, 135, ...?
15
3
5
9
To find the common ratio, divide any term by its previous term. Here, 15 ÷ 5 equals 3, which is consistent through the sequence.
Which of the following sequences is geometric?
10, 15, 20, 25
10, 6, 3.5, 1.75
10, 8, 6.4, 5.12
10, 5, 2.5, 1.25
A geometric sequence is formed by multiplying each term by a constant factor. In this case, every term is half of its predecessor, which makes the sequence geometric.
Find the missing term in the geometric sequence: 2, __, 8.
4
5
6
3
In a geometric sequence, the missing term is the geometric mean of the known terms. Since the geometric mean of 2 and 8 is √(2×8) = 4, the missing term is 4.
In the sequence 3, 9, 27, 81, ..., what is the position of the term 81?
6th
4th
3rd
5th
The sequence starts with 3 as the first term and each term is multiplied by 3. Counting the terms: 3 (1st), 9 (2nd), 27 (3rd), and 81 (4th) shows that 81 is the fourth term.
Determine whether the sequence 7, -7/3, 7/9, -7/27, ... is geometric.
Yes, with common ratio 1/3
No, it is arithmetic
Yes, with common ratio -1/3
No, it does not have a constant ratio
Dividing the second term by the first gives -1/3 and subsequent divisions yield the same ratio. This constant multiplication factor proves the sequence is geometric.
Find the common ratio for the sequence: -2, 6, -18, 54, ...?
3
2
-3
-2
The common ratio is determined by dividing any term by its preceding term. Here, 6 divided by -2 equals -3, a result that continues consistently in the sequence.
Calculate the 6th term of the geometric sequence: 4, 8, 16, 32, ...?
64
256
512
128
Using the formula a(n) = a₝ × r^(n-1) with a₝ = 4 and r = 2, the 6th term is calculated as 4 × 2^(5) = 128. This confirms the correct term in the sequence.
Which of the following sequences is NOT geometric?
5, 10, 15, 20
2, 6, 18, 54
3, -3, 3, -3
7, 21, 63, 189
A geometric sequence requires a constant multiplication factor between terms. The sequence 5, 10, 15, 20 increases by addition instead, making it arithmetic rather than geometric.
In a geometric sequence with first term 11 and common ratio 1/2, what is the fourth term?
11/16
11/4
11/2
11/8
The nth term of a geometric sequence is given by a(n) = a₝ × r^(n-1). Substituting a₝ = 11, r = 1/2, and n = 4, we get 11 × (1/2)³ = 11/8.
Find the sum of the first four terms of the geometric sequence: 3, 9, 27, 81.
120
100
108
130
By adding the terms 3, 9, 27, and 81, the total sum is 3 + 9 + 27 + 81 = 120. This simple addition confirms the correct sum for the sequence.
Determine the common ratio if the second term is 12 and the fifth term is 96 in a geometric sequence.
2
6
4
3
Using the relation a₅ = a₂ × r³, we find r³ = 96/12 = 8. Taking the cube root of 8 results in r = 2.
Which formula correctly represents the nth term of a geometric sequence?
a(n) = a₝ × r^(n-1)
a(n) = a₝ × (n-1)r
a(n) = a₝ × n
a(n) = a₝ + (n-1)r
The formula for the nth term of a geometric sequence is a(n) = a₝ × r^(n-1). Other formulas represent arithmetic sequences or are not standard for geometric progressions.
For the sequence 1, -2, 4, -8, ... what is the 5th term?
-16
16
8
-8
The common ratio for the sequence is -2. Thus, the 5th term is calculated as 1 × (-2)^(4) = 16, where the even exponent results in a positive term.
If the sum of the first three terms of a geometric sequence is 14, the first term is 2, and the common ratio is a positive integer, what is the common ratio?
3
1
4
2
Dividing the sum equation 2 + 2r + 2r² = 14 by 2 gives 1 + r + r² = 7. Solving the quadratic equation r² + r - 6 = 0, the positive integer solution is r = 2.
Determine the sum to infinity of the geometric series: 16, 8, 4, 2, ...?
16
32
48
64
For a convergent geometric series, the sum to infinity is calculated by a/(1 - r). Here, with a = 16 and r = 0.5, the sum is 16/(1 - 0.5) = 32.
If a geometric sequence has its fifth term equal to 243 and its second term equal to 9, and the common ratio is positive, what is the common ratio?
3
9
27
-3
Using the relation a₅ = a₂ × r³, we substitute the values to get 243 = 9 × r³. Solving for r³ gives 27 and thus r = 3, considering the positive constraint.
Find the value of n for which the nth term of a geometric sequence with first term 5 and common ratio 2 equals 320.
8
7
9
6
Using the formula a(n) = a₝ × r^(n-1), we set up the equation 5 × 2^(n-1) = 320. Dividing by 5 gives 2^(n-1) = 64, and recognizing that 64 = 2❶ leads to n - 1 = 6, or n = 7.
A geometric sequence has a common ratio of 0.5 and the sum of its first 5 terms is 31. What is the first term?
8
15
32
16
Using the sum formula Sₙ = a × (1 - r❿)/(1 - r) for n = 5 with r = 0.5, the equation becomes a × (1 - 0.5❵)/(0.5) = 31. This simplifies to a × (31/16) = 31, so solving for a gives 16.
Given that a geometric sequence has a positive common ratio and its second term is 9 while its fourth term is 81, determine the first term and the common ratio.
First term = 9, Common ratio = 3
First term = 9, Common ratio = 9
First term = 3, Common ratio = 3
First term = 3, Common ratio = 9
Since a₂ = a₝ × r = 9 and a₄ = a₝ × r³ = 81, dividing the two gives r² = 9, so r = 3 (considering only the positive solution). Thus, the first term is a₝ = 9/3 = 3.
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Study Outcomes

  1. Identify the common ratio in various geometric sequences.
  2. Determine whether a sequence is geometric based on its terms.
  3. Calculate the nth term of a geometric sequence using the common ratio.
  4. Analyze patterns within sequences to validate their geometric nature.

Geometric Sequences Cheat Sheet

  1. Geometric Sequence Basics - A geometric sequence is a list of numbers where each term is found by multiplying the previous one by the common ratio. This nifty pattern turns 2, 4, 8, 16 into a fun times-two dance! Keep an eye on that ratio and you'll unlock the magic of progression. OpenStax Deep Dive
  2. Spotting a Geometric Sequence - To check if a sequence is geometric, divide each term by its predecessor and see if you get the same juicy ratio every time. For example, 3, 6, 12, 24 gives 6÷3, 12÷6, 24÷12 all equal to 2 - boom! Got a constant quotient? You've got a geometric series. OpenStax Quick Check
  3. Nth-Term Formula - The nth term of a geometric sequence can be grabbed with a simple formula: aₙ = a₝ × r❿❻¹, where a₝ is the first term and r is the common ratio. Plug in your values and voilà! Instant access to any term in the sequence. Byju's Formula Guide
  4. Sum of First n Terms - To find the total of the first n terms, use Sₙ = a₝ × (1−r❿)/(1−r), as long as r isn't 1. This formula whisks you through sums like a math wizard without adding each number one by one. OpenStax Sum Formula
  5. Infinite Series Sum - If your ratio's absolute value is under 1 (|r|<1), you can sum an infinite geometric series with S∞ = a₝/(1−r). It's like capturing endless possibilities in one neat fraction! GeeksforGeeks Explained
  6. Finding the Common Ratio - Just divide any term by its preceding term to nail down the common ratio. For example, in 5, 15, 45, 135, you get r = 15/5 = 3 every time. Simple division opens up the sequence's secret. Symbolab How-To
  7. Recursive Definition - A geometric sequence can also be defined recursively: aₙ = r × aₙ₋₝, starting with a₝. This formula says "next term = ratio × previous term" and keeps the pattern rolling. Symbolab Recursive Guide
  8. Geometric Mean - The geometric mean between two numbers a and b is √(a×b). It gives a nice "middle ground" value in geometric contexts - perfect for growth rate estimates and more. GeeksforGeeks Mean Magic
  9. Real-World Applications - Geometric sequences pop up everywhere, from calculating population growth to modeling radioactive decay. Spot the ratio, apply the formula, and you're predicting the future like a pro! OpenStax Applications
  10. Practice Makes Perfect - The best way to master geometric sequences is by solving varied problems and checking your work. Challenge yourself with worksheets, quizzes, and real scenarios - your brain will thank you later! Symbolab Practice Hub
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