This is a great activity to encourage children to think about (and create) number rules. The focus is on practising calculations and identifying number patters.
Ask the children to work in pairs, give each child one of the Scrambled Number* sheets.
Each child now thinks of a rule involving one of the four operations. For example, "subtract 3". They then select a reasonable starting number on their Scrambled Number sheet and draw a circle around it. They apply their own rule to this number, find the answer, circle it and connect the two with an arrow. The same rule is applied again, until three numbers have been circled in a chain.
The example here shows (In orange) "add 13", starting with 7:
7 -----> 20 -----> 33
The players now swap sheets and they have to work out the rule from the three numbers they see circled. They then circle a fourth number and draw an arrow to it (46, in grey, in the example above).
This could be a simple race to see who is the first to identify the number pattern, best out of three... or it could develop into a discussion between the children regarding the merits of each different pattern.
After the children are used to the activity, you could encourage them to use more complex rules, such as: (n x 2) - 5
The Number Scramble sheets run from 1 to 50, if the children produce a number pattern that goes beyond 50 they could simply add the necessary numbers in the spaces on the sheet.
For some children, or as a demonstration, it may be useful to enlarge the sheets.
Clearly this is really a number-line activity, but scrambling the numbers hides the otherwise potentially easy-to-spot patterns, and forces the children to think through each calculation.
A further extension could involve making Scrambled Number sheets using different sequences of numbers: 50 - 100; 1,000 - 1,050; 0.01 - 0.5
Here's an image of the six A5 Number Scramble sheets with numbers 1 - 50: