Next, we will present some more complex sequences of numbers, including one of the most famous: the Fibonacci sequence.
The patterns of sequences vary from one to another.
Below, we present some examples of sequences with a different rule for each.
Note that the given rule can appear with: division, multiplication, addition, subtraction, or any combination of these.
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Examples of Sequences Exercise 1 2 , 4 , 8 , 16 , 32 2, 4, 8, 16, 32 2 , 4 , 8 , 16 , 32 In this sequence, to get from one term to the next we will multiply by 2 2 2 .
2 2 2
4 = 2 × 2 4=2\times2 4 = 2 × 2
8 = 2 × 4 8=2\times4 8 = 2 × 4
16 = 2 × 8 16=2\times8 16 = 2 × 8
And so on.
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Exercise 2 3 , 9 , 27 , 81 , 243 3, 9, 27, 81, 243 3 , 9 , 27 , 81 , 243 In this sequence, to get from one term to the next we need to multiply by 3 3 3 .3 3 3
9 = 3 × 3 9=3\times3 9 = 3 × 3
27 = 9 × 3 27=9\times3 27 = 9 × 3
81 = 27 × 3 81=27\times3 81 = 27 × 3
243 = 81 × 3 243=81\times3 243 = 81 × 3
And so on.
Exercise 3 6 , 4 , 2 , 0 , − 2 6, 4, 2, 0, -2 6 , 4 , 2 , 0 , − 2
In this sequence, to get from one term to the next we need to subtract 2 2 2 .
6 6 6
4 = 6 − 2 4=6-2 4 = 6 − 2
2 = 4 − 2 2=4-2 2 = 4 − 2
0 = 2 − 2 0=2-2 0 = 2 − 2
− 2 = 0 − 2 -2=0-2 − 2 = 0 − 2
Do you know what the answer is?
Exercise 4 1000 , 500 , 250 , 125 , 62.5 1000, 500, 250, 125, 62.5 1000 , 500 , 250 , 125 , 62.5 In this example, the operation used is division. In order to get from one term to the next, we divide the number by 2 2 2 .
1000 1000 1000
500 = 1000 : 2 500=1000:2 500 = 1000 : 2
250 = 500 : 2 250=500:2 250 = 500 : 2
125 = 250 : 2 125=250:2 125 = 250 : 2
62.6 = 125 : 2 62.6=125:2 62.6 = 125 : 2
Exercise 5 320 , 80 , 20 , 5 320, 80, 20, 5 320 , 80 , 20 , 5
The rule of this sequence is to divide each number by 4 4 4 to find the next number.
320 320 320
80 = 320 : 4 80=320:4 80 = 320 : 4
20 = 80 : 4 20=80:4 20 = 80 : 4
5 = 20 : 4 5=20:4 5 = 20 : 4
Exercises Try to work out the rule for each sequence:
1 , 3.75 , 6.5 , 9.25 , 12 1,3.75,6.5,9.25,12 1 , 3.75 , 6.5 , 9.25 , 12 7 , 49 , 343 , 2401 , 16807 7,49,343,2401,16807 7 , 49 , 343 , 2401 , 16807 0 , − 15 , − 30 , − 45 , − 60 , − 75 0,-15,-30,-45,-60,-75 0 , − 15 , − 30 , − 45 , − 60 , − 75 891 , 297 , 99 , 33 , 11 891,297,99,33,11 891 , 297 , 99 , 33 , 11 2 , 8 , 512 , 134217728 2,8,512,134217728 2 , 8 , 512 , 134217728
Review Questions What are sequences in mathematics? Sequences are ordered sets of numbers that follow a rule or pattern.
Do you think you will be able to solve it?
What is a sequence and a sequence rule? A sequence is a set of ordered numbers. The numbers follow a rule that tells us how to obtain the numbers of the sequence using the previous ones. Many times the rules are governed by the operations of addition, subtraction, multiplication, division, or some combination thereof.
What types of sequences are there in mathematics? There are many types of sequences. For example, increasing and decreasing sequences, in which the numbers are either increasing or decreasing and following a certain pattern. There are also very famous sequences that have their own name, such as the Fibonacci sequence. In this series, the two previous numbers must be added to obtain the next number.
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 1 + 1 = 2
2 + 1 = 3 2+1=3 2 + 1 = 3
3 + 1 = 4 3+1=4 3 + 1 = 4
Etcetera. Therefore, the next numbers missing in the sequence will be:8 + 1 = 9 8+1=9 8 + 1 = 9
10 + 1 = 11 10+1=11 10 + 1 = 11
Answer Exercise #2 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 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 94 + 2 = 96
96 + 2 = 98 96+2=98 96 + 2 = 98
98 + 2 = 100 98+2=100 98 + 2 = 100
and so forth......
Answer Exercise #3 The table shows the number of balls and the number of courts at the school:
2 4 6 1 2 3 Balls Courts
.
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 1 × 2 = 2
2 × 2 = 4 2\times2=4 2 × 2 = 4
3 × 2 = 6 3\times2=6 3 × 2 = 6
Therefore, the number of balls is 2 times greater than the number of courts.
Answer Exercise #4 Below is a sequence represented by squares. How many squares will there be in the 8th element?
Video Solution Step-by-Step Solution It is apparent, that for each successive number, a square is added in length and one in width.
Hence, the rule using the variable n is:
a ( n ) = n 2 a(n)=n^2 a ( n ) = n 2
Therefore, the eighth term will be:
n 2 = 8 × 8 = 16 n^2=8\times8=16 n 2 = 8 × 8 = 16
Answer Exercise #5 Below is the rule for a sequence written in terms of n n n :
2 n + 2 2n+2 2 n + 2
Calculate the value of the 11th element.
Video Solution Step-by-Step Solution We calculate by replacingn = 11 n=11 n = 11
2 × 11 + 2 = 2\times11+2= 2 × 11 + 2 =
First we solve the multiplication exercise and then we add 2:
22 + 2 = 24 22+2=24 22 + 2 = 24
Answer