You may have started looking at how to write rules to describe patterns with decimals and fractions. A general rule uses pronumerals, which are letters used to represent unknown values.

Watch this video to learn more about how to write general rules to describe patterns.

Worked examples

Question 1

Complete the pattern by adding $0.3$0.3 each time.

$0.4$0.4 $\editable{}$ $\editable{}$ $\editable{}$ $\editable{}$ $\editable{}$
If $b$b belongs to the same pattern, what is the next number?

Question 2

Consider the following pattern.

What is the pattern?

$6.3$6.3 $5.9$5.9 $5.5$5.5 $\editable{}$ $\editable{}$ $\editable{}$

The numbers are decreasing by $4$4.
A
The numbers are decreasing by $0.4$0.4.
B
The numbers are decreasing by $40$40.
C
The numbers are decreasing by $0.04$0.04.
D
Now complete the pattern.

$6.3$6.3 $5.9$5.9 $5.5$5.5 $\editable{}$ $\editable{}$ $\editable{}$
If $b$b belongs to the same pattern, what is the number after $b$b in the pattern?

Question 3

Complete the pattern by subtracting $\frac{1}{10}$110 each time.

$\frac{6}{10}$610 $\editable{}$ $\editable{}$ $\editable{}$ $\editable{}$ $\editable{}$
If $c$c belongs to the same pattern, what is the next number?

Outcomes

NA4-2

Understand addition and subtraction of fractions, decimals, and integers

NA4-9

Use graphs, tables, and rules to describe linear relationships found in number and spatial patterns

Generalising patterns using tenths or hundredths