How many seven digit numbers are there when 0,8, and 9 can not be the leading number?

Question

anonymous · Answer

seven digit numbers, not counting all 0's would be

1000000 to 9999999

anonymous · Answer

Okay, so is there a formula to figure this one out?

anonymous · Answer

So it's 7? What about different combinations of numbers?

anonymous · Answer

Well I was thinking that like 7894849 could be a number. so thus the answer would be a much larger number, but I might be misunderstanding the question. haha

anonymous · Answer

Starting from 1000000 to 1999999999, there are 999,999 numbers with a lead number of 1 so

7 x 999999 = 6,999,993

anonymous · Answer

999999 lead 1, 999999 lead 2, all the way to lead 7

I misunderstood before

anonymous · Answer

oh, okay. Thanks.

anonymous · Answer

wait

anonymous · Answer

Ok good, I thought I miscounted the number of numbers from 1000000 to 1999999

anonymous · Answer

actually, should it be 7,000,000...because I'm not sure if I counted each starting set (such as 1000000 and 2000000)

anonymous · Answer

I honestly have no idea, I'm pretty confused.

mathmate · Answer

If 0, 8, 9 are excluded...

mathmate · Answer

Then we can start with 1,2,3,4,5,6,7...only.

mathmate · Answer

How many 7-digit numbers can start with 1?
@bmo29

mathmate · Answer

starts from 1,000,000 to 1,999,999...

anonymous · Answer

Soo 7,000,000?

mathmate · Answer

You don't seem to be answering my question.
Is 7,000,000 for the final answer?

anonymous · Answer

No, is that how many can start with 1?

mathmate · Answer

Starting with 1, the smallest number is 1,000,000, and the largest number is 1,999,999.
How many numbers are there?

mathmate · Answer

If that sounds complicated, how many numbers are there from 10 to 19?

anonymous · Answer

9

mathmate · Answer

10,11,12,13,14,15,16,17,18,19
There are 10 numbers.
What you need to do is to subtract 10 from 19 but ADD 1 because both the first and last counts.
ok so far?

anonymous · Answer

Yes, so 10

mathmate · Answer

So how many numbers from 1,000,000 to1,999,999?

mathmate · Answer

In fact, we can do it in one single step,
how many numbers from 1,000,000 to 7,999,999?

anonymous · Answer

7,000,000

mathmate · Answer

That's the answer to your problem!
Well done!

anonymous · Answer

oh, wow! Thanks!

mathmate · Answer

You're welcome!  :)