Marco is putting some sweaters into storage for the winter. he has 10 sweaters, and he can fit 6 sweaters into a box. how many different groups of 6 sweaters can marco pack into a box?

Let us represent the slots of sweaters with dashes:
_ , _ , _ , _ , _ , _
The first slot has 10 possibilities, the next has 9, the next has 8 and so on.
10 x 9 x 8 x 7 x 6 x 5
= 151200 arrangements