# Dot chain sequences

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## Lesson details

### Key learning points

- In this lesson, we will learn how to group dot chains and generalise to find n-chains. We formulate calculations that represent dot chains.

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This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

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### 5 Questions

Q1.

What do we mean if we describe a sequence as "descending"?

The sequence is all negative numbers

The sequence is less important

Q2.

Which of the following is an example of a descending sequence?

-12, -10, -8, -6, ...

-5, -4, -3, -2, ...

3, 4, 5, 6, ...

Q3.

What is the nth term of 10, 8, 6, 4, 2, ...?

-2n + 8

2n + 12

2n + 8

Q4.

What is the nth term of -4, -7, -10, -13, ...?

-3n + 1

-4n + 7

3n - 7

Q5.

Find the first 5 terms of the sequence -5n + 2.

-5, -3, -1, 1, 3

-5, 2, 9, 18, 27

-7, -12, -17, -22, -27

### 5 Questions

Q1.

What is the tracking calculation for the grouping of this 3-chain?

27

8 + 8 + 1

9 x 3 + 1

Q2.

If the tracking calculation for this 3-chain is 8 x 3 + 1, what would the tracking calculation for a 20-chain?

20 x 3 + 1

8 x 3 + 20

Q3.

What is the tracking calculation for the grouping of this 3-chain?

3 x 6 + 3 +1

3 x 7 + 4

3 x 8 + 3 + 1

Q4.

If the tracking calculation for this 3-chain is 3 x 7 + 3 + 1, what would be the tracking calculation for an 100-chain?

100 x 7 + 100 + 1

100 x 7 + 4

3 x 100 + 100 + 1

Q5.

Using the grouping of this 3-chain, what is the tracking calculation for an n-chain? Write you answer as an algebraic expression.

3n + 1

3n + 8

n x 8 + 1