+0  
 
0
135
4
avatar+107 

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

 Dec 18, 2018
 #1
avatar
0

2+0+1+9 divide by how many there are which is 4

 

 so answer is 3

 Dec 18, 2018
 #2
avatar+98044 
+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

 

 

 

cool cool cool

 Dec 18, 2018
 #3
avatar+3994 
0

@CPhill, isn't the answer 433? 

tertre  Dec 19, 2018
 #4
avatar+4400 
+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

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