+107 What is the mean of all three digit positive integers whose digits are in the set {2, 0, 1, 9}?
+128407 We have these three digit numbers
102, 109, 120, 129, 190, 192, 201, 209, 210, 219, 290, 291,901, 910, ,902, 912, 920, 921
And their average is = 429 1/3
+6248 I got 433 as well.
I think the confusion stems from whether a digit can be repeated or not.
CPhil looks to be assuming they cannot.
There's nothing in the problem that states they can't.
The full list of numbers is
{200, 202, 201, 209, 220, 222, 221, 229, 210, 212, 211, 219, 290,
292, 291, 299, 100, 102, 101, 109, 120, 122, 121, 129, 110, 112, 111,
119, 190, 192, 191, 199, 900, 902, 901, 909, 920, 922, 921, 929, 910,
912, 911, 919, 990, 992, 991, 999}
and this has mean 433
