Sequences / Skips

🏆Practice sequences / skips up to 100

Sequences / Skips

When we have a sequence -
1) We read it from left to right
2) We understand if it's increasing or decreasing
3) We examine which digit type changes
4) We determine the pattern of the sequence
5) We complete the sequence according to the pattern that we discovered

Start practice

Test yourself on sequences / skips up to 100!

Complete the following sequence:

\( 1,3.\ldots \)

Practice more now

Sequences / Skips

What is an arithmetic sequence?

Numbers that come one after another with equal intervals between them.
The sequence can increase and the sequence can also decrease.

How can we determine whether the sequence is increasing or decreasing?

Always read the sequence from left to right! Just like reading a number.
Let's see what number it starts with and what number it ends with.
If the first number is smaller than the last number - there is an increase - ascending sequence
If the first number is larger than the last number - there is a decrease - descending sequence

Join Over 30,000 Students Excelling in Math!
Endless Practice, Expert Guidance - Elevate Your Math Skills Today
Test your knowledge

How can we determine what the pattern of the sequence is?

In order to discover a pattern, let's remember the rules we learned:
A number has ones, tens, and hundreds digits
For example -
57125712
22= ones digit
11 = tens digit
77 = hundreds digit
55= thousands digit

When we encounter a sequence - we ask ourselves -
In which digit did the change occur? Ones/Tens/Hundreds/Thousands
When we know which digit changed, we can immediately identify the intervals between the numbers and discover the pattern - adding or subtracting...
Let's look at a sample number sequence:
5,6,7,8,9,105,6,7,8,9,10
The sequence before us is an increasing sequence -
A sequence that starts at 55
and increases up to 1010.

There are intervals of 1 between each number 11
Therefore we can determine that:
The pattern of the sequence is 11.

Let's look at the following sequence:
13,15,17,1913,15,17,19

Let's check - whether the sequence increasing or decreasing -
The first number is 1313
and the last number is 1919
There is an increase, therefore the sequence is increasing.

Which digit changes? The ones digit.
How much does it change by each time? 22.
The pattern is – adding 22

Another example:
Let's explore the following sequence -
213,223,233,243,253213,223,233,243,253
Let's check if the sequence is increasing or decreasing
The first number is 213213
The last number is 253253
There is an increase hence the sequence is increasing.
Let's check in which digit the change occurs -
The change occurs in the tens digit
Each time 1010 is added
Therefore the pattern is - adding 1010.

Another example -
650,550,450,350650,550,450,350
Let's check if the sequence is increasing or decreasing -
The first number is 650650
The last number is 350350
There is a decrease hence the sequence is decreasing.
Let's check in which digit the change occurs and examine the change -
The change occurs in the hundreds digit - each time decreasing by 100100
Therefore the pattern is - subtraction of 100100

Now let's practice!
Look at the following sequence,
Complete it and determine:
Is the sequence increasing or decreasing?
What is its pattern?
102,___,122,132,142102, \_\_\_,122,132,142

Solution
Note –
In order to complete the sequence, we will first examine it and understand whether it is increasing or decreasing and what the pattern is.
We see that the first number in the sequence is 102102
and the last number in the sequence is 142142.
There is an increase, hence the sequence is increasing.
Now let's check from the numbers we have in which digit the change occurs – in the tens digit.
We can see that each time the number increases by 1010
Therefore- the pattern is adding 1010.
Now let's complete the sequence:
If we determined that the pattern is adding 1010, all we need to do is add 1010
to the number 102102
We obtain the following:
102+10=112102+10=112
Let's complete the sequence:
102,112,122,132,142102, {\underline{112}}, 122,132,142

Another exercise:
Complete the following sequence,
determine whether it is increasing or decreasing and indentify its pattern.
130,___,70,___,30,10130, \_\_\_, 70, \_\_\_,30,10

Solution:
First, let's understand whether the sequence is increasing or decreasing.
The first number in the sequence is 130130
The last number is 1010
There is a decrease, therefore the sequence is decreasing.

Let's examine in which digit the change occurs - the change occurs in the tens digit.
We observe that in every 2 numbers the number decreases by 2020.
Therefore, the pattern is - subtraction of 2020.
Now that we have discovered the pattern, all we need to do is complete the sequence.
In order to determine which number comes after 110110, we subtract 2020 and obtain :
11020=90110-20=90
In order to determine which number comes after 7070, we subtract 2020 and obtain the following:
7020=5070-20=50
Let's complete the sequence:
130,110,90,70,50,30,10130, 110, {\underline {90}}, 70, {\underline {50}}, 30, 10

Do you know what the answer is?

Examples with solutions for Sequences / Skips up to 100

Exercise #1

Complete the sequence:

1,113, 1,112, 1,111,  1{,}113,\ 1{,}112,\ 1{,}111, \ \ldots

Step-by-Step Solution

The given sequence is 1113,1112,1111 1113, 1112, 1111 .

Let's analyze the sequence:

  • The first term is 1113 1113 .
  • The second term is 1112 1112 , which is 11131 1113 - 1 .
  • The third term is 1111 1111 , which is 11121 1112 - 1 .

It's evident that each term is decreasing by 1 1 from the previous term. Therefore, this sequence is an arithmetic sequence with a common difference of 1-1.

Given this information, we can continue the sequence by subtracting 1 from the last given term, 1111 1111 .

  • The next term is 11111=1110 1111 - 1 = 1110 .
  • Following that, 11101=1109 1110 - 1 = 1109 .
  • Finally, 11091=1108 1109 - 1 = 1108 .

Thus, the next three terms in the sequence are 1110,1109, 1110, 1109, and 1108 1108 .

Looking at the provided options, choice 4: 1110,1109,1108 1110, 1109, 1108 , is the correct continuation of the sequence.

Answer

1,110, 1,109, 1,108 1{,}110,\ 1{,}109,\ 1{,}108

Exercise #2

Complete the sequence:

36,34 36,34\ldots

Step-by-Step Solution

To complete the given sequence 36,34, 36, 34, \ldots , we need to identify the pattern in the sequence. From the given terms, it appears that the sequence is decreasing.

Let's check if this is an arithmetic sequence, where each term decreases by a constant amount:

  • Subtract the second term from the first term: 3634=2 36 - 34 = 2 .
  • This indicates that each term is decreasing by 2.

Recognizing this pattern, the sequence can be continued by subtracting 2 from each subsequent term:

  • The next term after 34 is calculated as follows: 342=32 34 - 2 = 32 .
  • Continuing, the term after 32 is: 322=30 32 - 2 = 30 .
  • Finally, the term following 30 is: 302=28 30 - 2 = 28 .

Therefore, the complete sequence is 36,34,32,30,28 36, 34, 32, 30, 28 .

The correct answer choice, which matches this sequence, is:

36,34,32,30,28 36,34,32,30,28

Answer

36,34,32,30,28 36,34,32,30,28

Exercise #3

Complete the sequence:

20,155, 20,154, 20,153,  20{,}155,\ 20{,}154,\ 20{,}153, \ \ldots

Step-by-Step Solution

To complete the sequence 20,155,20,154,20,153, 20{,}155, 20{,}154, 20{,}153, \ldots , follow these steps:

  • Step 1: Identify the sequence pattern.
  • Step 2: Notice that each term decreases by 1 from the previous term.
  • Step 3: Continue the pattern by subtracting 1 from the last known term.

Let's work through the steps:

Step 1:
The sequence given is: 20,155,20,154,20,153, 20{,}155, 20{,}154, 20{,}153, \ldots .
Step 2:
Observe that the first term 20,155 20{,}155 is reduced to 20,154 20{,}154 , then to 20,153 20{,}153 , establishing a pattern of subtracting 1.
Step 3:
Using this pattern, find the next terms:
From 20,153 20{,}153 , subtract 1 to get 20,152 20{,}152 .
From 20,152 20{,}152 , subtract 1 to get 20,151 20{,}151 .
From 20,151 20{,}151 , subtract 1 to get 20,150 20{,}150 .

Therefore, the sequence continues as follows: 20,152,20,151,20,150 20{,}152, 20{,}151, 20{,}150 .

Answer

20,152, 20,151, 20,150 20{,}152,\ 20{,}151,\ 20{,}150

Exercise #4

Complete the following sequence:

20,,24,26, 20,\ldots,24,26\ldots ,\ldots

Step-by-Step Solution

To solve the problem of completing the sequence 20,,24,26,, 20, \ldots, 24, 26, \ldots, \ldots , we recognize the sequence's underlying pattern.

Step 1: Analyze known terms.
The given sequence begins with 20,,24,26,, 20, \ldots, 24, 26, \ldots, \ldots . Notice the known terms 20 20 and 24 24 , and 26 26 .

Step 2: Determine the difference between known terms.
The difference between 24 24 and 20 20 is 4 4 , suggesting an ongoing pattern.
Between 26 26 and 24 24 , the difference is 2 2 , proposing alternation in differences or a complete oversight of interspersed terms around 26 26 .

Step 3: Determine full sequence consistency.
Check if numbers align with a two-step even-number sequence, which implies adding 2 2 successively.
Extending forward and back confirms 20,22,24,26,28, 20, 22, 24, 26, 28, \ldots .

Step 4: Verification considering other instructions.
The sequence appears to be a straightforward arithmetic one comprising purely even numbers beginning from 20 20 . This step requires confirming subsequent numbers 28,30 28, 30 .

Conclusion: Sequential confirmation proves the arithmetic nature of the understanding, yielding:

20,22,24,26,28,30 20,22,24,26,28,30

Answer

20,22,24,26,28,30 20,22,24,26,28,30

Exercise #5

Complete the following sequence:

25,,21,19,, 25,\ldots,21,19,\ldots,\ldots

Step-by-Step Solution

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

  • Step 1: Determine the common difference by looking at the known terms, 21 and 19.
  • Step 2: Apply the common difference to find the missing terms in the sequence.
  • Step 3: Verify the sequence pattern to ensure accuracy.

Now, let's work through each step:

Step 1: The common difference between 21 and 19 is 2. Thus, each number in the sequence is reduced by 2 from the previous one.

Step 2: Starting from 25, subtract 2 to fill in the first gap: 252=23 25 - 2 = 23 . Now the sequence is 25, 23, ..., 21, 19.

From 19, subtract 2 to fill in the next gap: 192=17 19 - 2 = 17 , then 172=15 17 - 2 = 15 . Thus, the complete sequence is:

25,23,21,19,17,15 25, 23, 21, 19, 17, 15

Therefore, the solution to the problem is 25,23,21,19,17,15 25, 23, 21, 19, 17, 15 .

Answer

25,23,21,19,17,15 25,23,21,19,17,15

Start practice