How many pairs of numbers add up to 11? l have used calculation find their is 6 pairs but like to know • how could i change how i originally did this activity (include resources and mathematics used)?

 If all numbers are greater than zero and no repeated numbers exist these are the 5 possible combinations:

 1 + 2 + 8
 1 + 3 + 7
 1 + 4 + 6
 2 + 3 + 6
 2 + 4 + 5. 
 

If one number is allowed to be zero and no repeated numbers exist these are 5  combinations:
 0 + 11
1 + 1 + 9
 2 + 2 + 7
3 + 3 + 5
 4 + 4 + 3
5 + 5 + 1

Hope this helps