From 10000 to 11000, digit 5 will appear from 10000 to 10999 only.
Basically, you need to count 5 appear from 0 to 999.
From 0 to 99, five appear 20 times.
from 100 to 199 = 20 times.
from 200 to 299 = 20 times.
From 300 to 399 = 20 times.
from 400 to 499 = 20 times.
from 500 to 599 = 20+ 100= 120 times.
from 600 to 699 = 20 times
from 700 to 799 = 20 times.
from 800 to 899 = 20 times.
from 900 to 999 = 20 times.

So total from 1 to 1000, 5 digit appears 300 times.

This is one of the method.

From 500 - 599
500 = 1 time
501 = 2 time
502 = 3 time
503 = 4 time
.
.
.
.
599 = 100 time

0 - 9 = 10 time
50 -59 = 10 with 55 count as 1

1000÷5=200
It should be this