What is a Sequence?

Mathematical sequences are a group of terms with a certain rule that dictates a certain operation must be performed and repeated in order to get from one term to the next.
The operation can be addition, subtraction, multiplication, division, or any other mathematical operation.

For example, the following is a basic numerical series:
1,2,3,4,5 1, 2, 3, 4, 5

To get from one term to the next in the sequence we add +1 +1 .
2=1+1 2 = 1+1
3=2+1 3 = 2+1
4=3+1 4 = 3+1
And so on.

Comparison of sequences: The arithmetic sequence starts at -6 and increases by 7 each time (-6, 1, 8, 15, 22). The geometric sequence starts at 1 and multiplies by 3 each time (1, 3, 9, 27, 81). Arrows indicate the operation between term


Practice Series / Sequences

Examples with solutions for Series / Sequences

Exercise #1

12 ☐ 10 ☐ 8 7 6 5 4 3 2 1

Which numbers are missing from the sequence so that the sequence has a term-to-term rule?

Video Solution

Step-by-Step Solution

It is possible to see that there is a difference of one number between each number.

That is, 1 is added to each number and it will be the next number:

1+1=2 1+1=2

2+1=3 2+1=3

3+1=4 3+1=4

Etcetera. Therefore, the next numbers missing in the sequence will be:8+1=9 8+1=9

10+1=11 10+1=11

Answer

11 , 9

Exercise #2

Is there a term-to-term rule for the sequence below?

18 , 22 , 26 , 30

Video Solution

Step-by-Step Solution

To solve this problem, we'll check the differences between consecutive terms:

  • The difference between 2222 and 1818 is 2218=422 - 18 = 4.
  • The difference between 2626 and 2222 is 2622=426 - 22 = 4.
  • The difference between 3030 and 2626 is 3026=430 - 26 = 4.

All differences between consecutive terms are 44, indicating a constant increment. Thus, the sequence is arithmetic with a common difference of 44.

The term-to-term rule is: to get the next term, add 44 to the current term.

Therefore, yes, there is a term-to-term rule for this sequence, given by adding 44 to the previous term.

Answer

Yes

Exercise #3

Look at the following set of numbers and determine if there is any property, if so, what is it?

1,2,3,4,5,6 1,2,3,4,5,6

Video Solution

Step-by-Step Solution

To solve this problem, we need to determine if there's a consistent pattern or rule in the sequence 1,2,3,4,5,61, 2, 3, 4, 5, 6.

Let's proceed step by step:

  • Step 1: Analyze the given sequence
    The sequence is 1,2,3,4,5,61, 2, 3, 4, 5, 6.
  • Step 2: Check for a common difference
    Calculate the difference between each consecutive pair of numbers:

21=12 - 1 = 1
32=13 - 2 = 1
43=14 - 3 = 1
54=15 - 4 = 1
65=16 - 5 = 1

From the calculations above, we observe that the difference between each consecutive term is +1+1.

Conclusion: The sequence is an arithmetic sequence with a common difference of +1+1.

Therefore, the correct choice is +1 +1 .

Answer

+1 +1

Exercise #4

Look at the following set of numbers and determine if there is any property, if so, what is it?

10,8,6,4,2 10,8,6,4,2

Video Solution

Step-by-Step Solution

To solve this problem, we need to analyze whether the set of numbers 10,8,6,4,2 10, 8, 6, 4, 2 has a pattern or property.

  • Step 1: Observe the difference between consecutive terms:
    810=2 8 - 10 = -2
    68=2 6 - 8 = -2
    46=2 4 - 6 = -2
    24=2 2 - 4 = -2
  • Step 2: Analyze the result.
    We see that the difference between consecutive terms is consistently 2-2.

This indicates that the terms form an arithmetic sequence with a common difference of 2-2.

Hence, the property of this set of numbers is that it is an arithmetic sequence with a common difference of 2 -2 .

By comparing the possible answer choices, we confirm that the correct choice is number 1: 2 -2 .

Answer

2 -2

Exercise #5

Look at the following set of numbers and determine if there is any property, if so, what is it?

94,96,98,100,102,104 94,96,98,100,102,104

Video Solution

Step-by-Step Solution

One can observe that the difference between each number is 2.

That is, with each leap the next number increases by 2:

94+2=96 94+2=96

96+2=98 96+2=98

98+2=100 98+2=100

and so forth......

Answer

+2 +2

Exercise #6

Look at the following set of numbers and determine if there is any property, if so, what is it?

13,16,20,23 13,16,20,23

Video Solution

Step-by-Step Solution

To solve this problem, we'll check for consistent differences between the numbers, as this can indicate a property such as an arithmetic sequence.

  • Step 1: Calculate the difference between each pair of consecutive numbers.

Let's look at the differences:

1613=3 16 - 13 = 3

2016=4 20 - 16 = 4

2320=3 23 - 20 = 3

  • Step 2: Analyze the differences.

The differences between consecutive numbers are not consistent: 3,4, 3, 4, and 3 3 .

This irregularity shows that there is no single property like a consistent common difference, which would indicate an arithmetic sequence.

Therefore, no particular property applies to this set as a whole based on the differences analyzed.

The correct choice is that a regular property does not exist among these numbers.

Therefore, the solution to the problem is: Does not exist.

Answer

Does not exist

Exercise #7

Look at the following set of numbers and determine if there is any property, if so, what is it?

13,10,7,4,1 13,10,7,4,1

Video Solution

Step-by-Step Solution

To solve this problem, we will determine if the given sequence of numbers follows a particular pattern or property:

First, we list the sequence provided: 13,10,7,4,113, 10, 7, 4, 1.

Since an arithmetic sequence is one of the simplest patterns, we will check for a common difference, which involves subtracting each term from the next:

  • Calculate the difference between the first and second terms: 1013=310 - 13 = -3.
  • Calculate the difference between the second and third terms: 710=37 - 10 = -3.
  • Calculate the difference between the third and fourth terms: 47=34 - 7 = -3.
  • Calculate the difference between the fourth and fifth terms: 14=31 - 4 = -3.

We observe that the difference between each consecutive pair of numbers is consistently 3-3. This implies that the sequence has a common difference of 3-3, and therefore, it is an arithmetic sequence.

In conclusion, the identified property for the sequence is that it is an arithmetic sequence with a common difference of 3 -3 .

Therefore, the solution to the problem is 3 -3 .

Answer

3 -3

Exercise #8

Look at the following set of numbers and determine if there is a rule. If there is one, what is it?

5,10,15,20,25,30 5,10,15,20,25,30

Video Solution

Step-by-Step Solution

To solve this problem of finding the rule for the sequence 5,10,15,20,25,30 5, 10, 15, 20, 25, 30 , we will follow these steps:

  • Step 1: Analyze the difference between consecutive numbers in the sequence.
  • Step 2: Identify a consistent pattern or rule.
  • Step 3: Compare the pattern against the given multiple-choice answers.

Now, let's work through each step:

Step 1: Calculate the difference between consecutive terms:

105=510 - 5 = 5

1510=515 - 10 = 5

2015=520 - 15 = 5

2520=525 - 20 = 5

3025=530 - 25 = 5

Step 2: We observe that the difference between each pair of successive numbers is 55, which is consistent throughout the sequence.

Step 3: Compare this pattern with the given choices. The choice corresponding to adding 5 consistently matches our observed pattern.

Therefore, the rule for this sequence is to add 5 to each preceding number to obtain the next number in the sequence. This corresponds with choice number 2: +5 +5 .

Answer

+5 +5

Exercise #9

The table shows the number of balls and the number of courts at the school:

246123BallsCourts

.

Complete:

Number of balls is _________ than the number of courts

Video Solution

Step-by-Step Solution

It is possible to see that if you multiply each number from the right column by 2, you get the number from the left column.

That is:1×2=2 1\times2=2

2×2=4 2\times2=4

3×2=6 3\times2=6

Therefore, the number of balls is 2 times greater than the number of courts.

Answer

2 times greater

Exercise #10

Look at the following set of numbers and determine if there is any property, if so, what is it?

2,4,8,16,32,64 2,4,8,16,32,64

Video Solution

Step-by-Step Solution

To solve this problem, let's analyze the sequence of numbers given: 2,4,8,16,32,64 2, 4, 8, 16, 32, 64 .

First, let's calculate the ratio between each pair of consecutive terms in the sequence:

  • The ratio of the second term 4 4 to the first term 2 2 is 42=2\frac{4}{2} = 2.
  • The ratio of the third term 8 8 to the second term 4 4 is 84=2\frac{8}{4} = 2.
  • The ratio of the fourth term 16 16 to the third term 8 8 is 168=2\frac{16}{8} = 2.
  • The ratio of the fifth term 32 32 to the fourth term 16 16 is 3216=2\frac{32}{16} = 2.
  • The ratio of the sixth term 64 64 to the fifth term 32 32 is 6432=2\frac{64}{32} = 2.

Each consecutive term is obtained by multiplying the previous term by 2 2 . Therefore, this sequence is a geometric sequence where each term is ×2\times 2 times the preceding term.

This consistent multiplication factor shows that the sequence's property is that of a geometric progression with a common ratio r=2 r = 2 .

In conclusion, the identified property of the sequence is that each term is multiplied by 2 2 , which is option ×2 \times 2 .

Answer

×2 \times2

Exercise #11

Look at the following set of numbers and determine if there is any property, if so, what is it?

1,3,9,26,81 1,3,9,26,81

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Check if the sequence is an arithmetic sequence.
  • Step 2: Check if the sequence is a geometric sequence.
  • Step 3: Explore other patterns if neither arithmetic nor geometric sequence fits.

Now, let's work through each step:

Step 1: Checking for arithmetic sequence:
To be an arithmetic sequence, the difference between consecutive terms should be constant.
For 1,3,9,26,811, 3, 9, 26, 81:
31=23 - 1 = 2
93=69 - 3 = 6
269=1726 - 9 = 17
8126=5581 - 26 = 55
The differences are not the same, so it is not an arithmetic sequence.

Step 2: Checking for geometric sequence:
To be a geometric sequence, the ratio of consecutive terms should be constant.
For 1,3,9,26,811, 3, 9, 26, 81:
31=3\frac{3}{1} = 3
93=3\frac{9}{3} = 3
269\frac{26}{9} is not 3, similarly 8126\frac{81}{26} is not constant.
Thus, it is not a geometric sequence either.

Step 3: Explore other non-trivial patterns:
Without straightforward arithmetic or geometric patterns identified, try other patterns or sequences, but given the options provided, none of the numerical patterns visibly connect through such standard sequences. This suggests examining deeper provides diminishing returns without knowing additional context or rules that these numbers follow.

Evaluating choices: None of the options directly covers a standard pattern or rule fitting all these points consistently, indicating no obvious, identical property unifies the set.

Therefore, the correct answer is Does not exist, as there isn't an evident mathematical property or pattern connecting these numbers uniformly.

Answer

Does not exist

Exercise #12

Look at the following set of numbers and determine if there is any property, if so, what is it?

100,50,25,10,20 100,50,25,10,20

Video Solution

Step-by-Step Solution

Therefore, the solution to the problem is Does not exist.

Answer

Exercise #13

Look at the following set of numbers and determine if there is any property, if so, what is it?

256,64,16,4,1 256,64,16,4,1

Video Solution

Step-by-Step Solution

To identify the property of the sequence 256,64,16,4,1 256, 64, 16, 4, 1 , we'll calculate the ratio between each consecutive pair of terms:

  • First, calculate the ratio of the second term to the first term: 64256=14 \frac{64}{256} = \frac{1}{4} .
  • Next, calculate the ratio of the third term to the second term: 1664=14 \frac{16}{64} = \frac{1}{4} .
  • Then, calculate the ratio of the fourth term to the third term: 416=14 \frac{4}{16} = \frac{1}{4} .
  • Finally, calculate the ratio of the fifth term to the fourth term: 14=14 \frac{1}{4} = \frac{1}{4} .

All calculated ratios are equal to 14 \frac{1}{4} . This confirms that each term in the sequence is obtained by multiplying the previous term by 14 \frac{1}{4} or equivalently, multiplying by 0.25.

Therefore, the sequence follows the property of being a geometric sequence with a common ratio of 0.25 0.25 .

This corresponds to the answer choice: ×0.25 \times 0.25 (Choice 4).

Answer

×0.25 \times0.25

Exercise #14

Look at the following set of numbers and determine if there is any property, if so, what is it?

12,24,35,48,60 12,24,35,48,60

Video Solution

Step-by-Step Solution

To solve this problem, we'll inspect the differences between consecutive numbers:

First, calculate the differences:

  • 2412=12 24 - 12 = 12
  • 3524=11 35 - 24 = 11
  • 4835=13 48 - 35 = 13
  • 6048=12 60 - 48 = 12

The differences are 12,11,13, 12, 11, 13, and 12 12 .

We observe that there is no consistent pattern or common difference in these numbers, which implies the numbers do not form a regular arithmetic or geometric sequence.

Therefore, the property does not consistently exist across all numbers.

Consequently, the solution to this problem is that a common property does not exist.

Answer

Does not exist

Exercise #15

Look at the following set of numbers and determine if there is any property, if so, what is it?

4,8,12,5,20 4,8,12,5,20

Video Solution

Step-by-Step Solution

To solve this problem, we will investigate whether the sequence of numbers 4,8,12,5,204, 8, 12, 5, 20 possesses any identifiable pattern or property, focusing primarily on identifying an arithmetic pattern.

Let's examine the differences between consecutive terms:

  • The difference between 88 and 44 is 84=48 - 4 = 4.
  • The difference between 1212 and 88 is 128=412 - 8 = 4.
  • The difference between 55 and 1212 is 512=75 - 12 = -7.
  • The difference between 2020 and 55 is 205=1520 - 5 = 15.

We observe that the differences between consecutive numbers are not consistent. Since the sequence does not exhibit a constant difference, it is not an arithmetic sequence.

We could also consider checking for a geometric pattern, but since immediate calculations show variations in both differences and potential ratios, this seems unnecessary for a basic sequence like this.

None of the properties we considered (arithmetic or geometric) apply. Thus, we conclude there is no identifiable pattern or property consistent across the entire sequence of numbers 4,8,12,5,204, 8, 12, 5, 20.

Therefore, the correct answer is: Does not exist.

Answer

Does not exist

Topics learned in later sections

  1. Recurrence Relations