Need help with grouping formula

[Rocky100]

Hi, I am new to this and only have basic excel skills but l want to know how after I have added 2 columns of numbers together and got the averages, I then want to sort the average column from smallest to largest and split them into 1 sec division, with 3 divisions.
so say number x ran a race of 19.500 and second time of 20.500, the average would be 20.000 and now that would set the fastest time for division one with 1 second splits. I want the formula to group all runners who ran an average between 20.000 and 21.000 and then set division 2 as anyone between 21.001 and 22.001 and division 3 22.002 and over.
Hope this makes sense and someone can help me...