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Sequences

Sequences

Assessment

Presentation

Mathematics

6th - 8th Grade

Easy

Created by

Jan Steele

Used 4+ times

FREE Resource

11 Slides • 21 Questions

1

Sequences

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2

What do I already know about Sequences?

  • Do I know any 'famous' number sequences?

  • Do they have special names?

  • How are the terms generated? Are they related to each other or to a special rule?

3

Multiple Select

The Triangular numbers are

1

1, 8, 27, 64, ......

2

1, 3, 6, 10, .......

3

2, 4, 6, 8, .......

4

1, 3, 5, 7, ....

5

1, 4, 9, 16,......

4

Multiple Select

The cube numbers are

1

1, 1, 2, 3, 5,.....

2

2, 4, 6, 8,......

3

1, 8, 27, 64,.....

4

1, 3, 5, 7,......

5

1, 3, 6, 10,.....

5

Multiple Select

The even numbers are

1

1, 3, 6, 10,...

2

1, 8, 27, 64,....

3

1, 4, 9, 16,....

4

2, 4, 6, 8,.....

5

1, 1, 2, 3, 5,....

6

Multiple Select

The odd numbers are

1

1, 3, 5, 7,.....

2

1, 1, 2, 3, 5,..

3

2, 4, 6, 8,....

4

1, 8, 27, 64,.....

5

1, 4, 9, 16,....

7

Multiple Select

The Fibonacci numbers are

1

1, 3, 6, 10,....

2

1, 8, 27, 64,......

3

2, 4, 6, 8,.....

4

1, 1, 2, 3, 5,......

5

1, 4, 9, 16

8

Open Ended

For the odd/even numbers, how is the sequence generated?

9

Open Ended

For the square numbers, how is the sequence generated?

10

Open Ended

Question image

Why are the numbers called ‘square’?

Could we represent the sequence in diagram form?

11

Open Ended

Triangular numbers, how is the sequence generated?

12

Open Ended

Question image

Why are the numbers called ‘cube’? Could we represent

the sequence in diagram form?

13

Open Ended

Fibonacci numbers, how is the sequence generated?

14

Open Ended

Is there a link between the term number and the terms of the

sequence? Careful. This one is tricky!

15

Open Ended

Is this a term-to-term rule? How could I work out the

100th term without writing out all 100 terms?

16

Open Ended

Is there a rule relating to the position of the term I

am looking for?

17

Types of Sequences

  • Arithmetic

  • Geometric

  • Neither

18

Types of Sequences (cont.)

An arithmetic sequence changes by adding or subtracting the same amount each time, 

eg 3, 6, 9, 12, …. or 12, 10, 8, 6, …. 


A geometric sequence changes by multiplying or dividing by the same amount each time, 

eg 3, 6, 12, 24, …. or 100, 50, 25, 12.5, … 


Sequences can be either arithmetic or geometric or neither. 

19

So, what types were the sequences above?

  • Arithmetic – odd numbers, even numbers


  • Geometric - none of these

  • Neither - Fibonacci, triangular, square, cube

20

Term-to-Term & Position-to-Term Rules

Sequences can be defined using a term-to-term rule. 


Each term is generated from the previous term using the rule. 



What term-to-term rules might we use? 

21

Open Ended

Generate at most 2 sequences of your own and state whether they are:


- Arithmetic


OR


-Geometric

22

Position - to - Term

A position-to-term rule describes each term of the sequence in relation to its position in the sequence. 


This rule can be given in words or in algebra. 


The position is usually denoted by the letter n so if we want the 10th term, we would put n = 10 into a formula. 


23

For example 2, 4, 6, 8, 10, .… is obtained by doubling the term number 
Term 1 =  2×12\times1  
Term 2 =  2×22\times2  
Term 3 =  2×32\times3  
Term 4 =  2×42\times4   etc. 
So a formula for the nth term would be  2×n2\times n  or  2n2n  

24

Using a table:

Position number  1    2    3    4    5
Term                     2    4    6    8   10


25

Open Ended

1. What would be the  17th17^{th}  term of this sequence?





2. Is 103 in this sequence?




3. What is the position of the term 84?

26

The answers are:


- 17th term is  2×172\times17   = 34 

- 103 is not in the sequence as all the numbers are even. 
The term number for 103 would have to be 103 ÷ 2 = 51.5 and this is not possible as position numbers have to be whole numbers 

- 84 ÷ 2 = 42 so it is the 42nd term. 

27

Open Ended

Write out the position-to-term rule, in words, for each of the following sequences listed below:

a) 5, 10, 15, 20,....

b) 13, 26, 39, 52,....

c) 2, 5, 8, 11,.....

For each sequence above, answer the following questions:
i) What is the  50th50^{th}  term?


ii) Is the number 60 in the sequence? How do you know?

iii) Can the rule be written in algebra?

28

The answers are: 


a) 5, 10, 15, 20, …. ‘multiply position number by 5’  5n5n  

b) 13, 26, 39, 52, .… ‘multiply position number by 13’  13n13n  
 
c) 2, 5, 8, 11, …. ‘multiply position number by 3 then subtract 1’  3n13n-1  

29

Open Ended

Write the first four terms for the sequence below:


'An arithmetic sequence with a difference of two between the terms'

30

Open Ended

Write the first four terms for the sequence below:


'A geometric sequence in which the next term is double the previous term'

31

Open Ended

Write the first four terms for the sequence below:


'An arithmetic sequence involving fractions'

32

Open Ended

Write the first four terms for the sequence below:


'A geometric sequence involving division'

Sequences

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