it'sSarah must be new here...
6 

Partitioning a set 
Partitioning a set
Hey, I'm afraid the new solution isn't right either. Let's take a look at your own example: you divided those numbers like: {1,2}, {3,4}, {5,6}, {7,8} at the first line. What I say is, imagine we have {1,2} and {3,4}. this way, we can have these combinations for other sets: (1.) {5.6}, {7.8} (2.) {5.7},{6.8} (3.) {5.8},{6.7}. You didn't put all the examples there. it's true for all other lines... and other combinations! Now, we know that k divides r. let q = r/k to make it simple. We want to put r distinct objects into q indistinct groups, k objects in each. to make our work easier, we also take the groups distinct. so we take k objects for group#1, k for #2, and so on, which will be: C( qk , k ) * C( (q1)k , k ) * ... * C ( k , k ) Since the groups are actually indistinct, we should now divide this by q! cause we have counted each combination q! times. well that's the way I think the problem should be solved context 