at the beginning, there are 15 pigs without ribbons. one of the pigs receives a ribbon. how many are left ribbonless?
14. when another pig is given a ribbon, there are 13 left. after all the ribbons have been given out, 3 of the 15 pigs have ribbons.
if any one of the 15 at the beginning is given a ribbon, there are 15 possible combos. for the second ribbon, there are 14 combos- but each of those combos has to go through the first 15. for the third ribbon, there are 13 combos, going through 14 and 15.
simply put, 15 x 14 x 13.
