3 ms·

For calculating the number of combinations, it looks like they are simply using 100 choose 7, or C(100, 7) which yields 16,007,560,800. http://what-are-the-cha

• psychometry 12y ago
  That doesn't take into account repeated letters. You actually want the number of 7-combinations of the multiset { A * 5, B * 3, C * 4, ... } or whatever the letter frequencies are. That's for the first draw from the bag.