Question 1208708
<pre>
We will count the 7s among the thousands place digits,
then the hundreds place digits, then the tens place digits,
and finally the one-place digits.

There are no 7's among the thousands place digits.

Among the hundreds place digits,

700-799 account for 100 hundreds place 7s,
1700-1799 account for 100 hundreds place 7s,
2700-2710 account for 11 hundreds place 7s

That's 211 7s among the hundredths place digits.

70-79 account for 10 tens place 7s
170-79 account for 10 tens place 7s
...
2670-2679 account for 10 tens place 7s

That's 27x10=270 7s among the tens place digits.

[Note: from 2680 through 2710 there are no 7s in tens places.]

The 7s in ones digits occur in 7,17,27,37,...2697,2707 

That's an arithmetic sequence with a1=7, an=2707, d=10
We find the number of terms:

{{{a[n]=a[1]+(n-1)d}}}
{{{2707=7+(n-1)10}}}
{{{2707=7+10n-10}}}
{{{2710=10n}}}
{{{271=n}}}

Sum total= 211+270+271=752

There are 752 7s in all the page numbers.

Edwin</pre>