Suppose you have an apple, an orange, a banana, a pineapple a grape and a screwdriver and you choose to take exactly 3 of these things. This is called a 3-combination of a 6-set, because you chose 3 of the 6 things. Now suppose you want a different set of 3 things by putting one thing back and taking another. Easy, right?
For some inexplicable reason, however, you want to hold every set of three things exactly once and each time you change, you want to swap one item in your hand for one on the table. Is this even possible?!?
The short answer is yes. And I’ve animated it for you! Look at it like this: The colour of the balls in the animation indicates whether the thing in that position has been chosen. Swapping a red ball in position 2 and a blue ball in position 6 simply indicates that the second item was swapped with the fifth item.
Without further ado, enjoy my first ever flash animation.