Intermediate algebra

[Gail Price]

Find the sum of all seven-digit numbers that can be written using only ones and zeros. I do not totally understand this problem.

 

[Loren]

If it said "Find the sum of all two-digit numbers that can be written using only ones and zeros" you COULD respond as...

00+01+10+11 = 22.

If it said "Find the sum of all three-digit numbers that can be written using only ones and zeros" you MIGHT respond as...

000+001+010+100+011+101+110+111=444.

If it said "Find the sum of all four-digit numbers that can be written using only ones and zeros" your response could be...
0000
0001
0010
0100
1000
0011
0101
0110
1001
1010
1100
0111
1011
1101
1110
1111
8888

Mmmm. Maybe there's a pattern to look for.
For two digits we get four addends.
For three digits we get eight addends.
For four digits we get sixteen addends.
Good luck.

 

[Gail Price]

I think I know what he wants now, thank you