How many 11 -digit positive integers can be written using only the digits 1,2 and 3 and have exactly three 1’s and exactly two 2's as digits?
Combinations ==(1, 1, 1, 2, 2, 3, 3, 3, 3, 3, 3)==1 combination
Permutations ==11! / [6!*2!*3!] ==4,620 permutations.
