What is the mean of all three digit positive integers whose digits are in the set {2, 0, 1, 9}?

MacTyBoys Dec 18, 2018

#2**+3 **

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

CPhill Dec 18, 2018

#4**+1 **

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

Rom
Dec 19, 2018