Math Help - Need Help.

1. Need Help.

There are 24 four-digit numbers that can be formed by permuting 3, 5, 7, and 9. What is the sum of all these numbers?

2. Re: Need Help.

Originally Posted by ConnieLam
There are 24 four-digit numbers that can be formed by permuting 3, 5, 7, and 9. What is the sum of all these numbers?
I don't know how much this will help but here's your answer. I just brute forced it. There's probably a more elegant way.

Ok, here's a more elegant way.

Each digit will appear in each 10's place 6 times. Thus the total is

$6\times (3+5+7+9)(1000+100+10+1) = 159984$

3. Re: Need Help.

Thanks. You helped a lot.