Choose a 2-digit number where the difference between the two digits in that number is 2 for example 24. 

Reverse that number and take the smaller number away from the bigger number.

42 subtract 24 = ?

What do you notice about the final answer when the difference between the digits is 4?

Can you predict what the final difference will be when the difference between the digits is 8?

Try this subtraction investigation:

Write down a 3-digit number, say      742

Reverse the digits                             472

Subtract                                           495

Reverse the digits                             594

Add                                                 1089

Do you always get 1089?

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Key Stage 1:

Take any two numbers and make a number chain with a rule.

Can you make a number chain using this rule?

Take any two numbers, for example 12 and 5.

Take the positive difference of the last two numbers to make the next number.  Then continue to do this as shown,

12,5Þ7Þ2Þ5Þ3…………………