Consecutive numbers are numbers that are in order, like 123456789.

When U add consecutive numbers you write the numbers your using in order from least to greatest. Then you add the two outside numbers which would be the 9 and 1 for me. then work your way to the middle(I would go to
the 2 and 8, then the 3 and 7 etc.). If you have two odd numbers you will have a leftover,and you add that number too
the others.