Math

There are: 10 in between 100 and 200=100,110,120,130.........190, which are multiples of 10.

Therefore, there are: 100 - 10 =90, which are NOT multiples of 10: So that we have:

10 x 100 =100, between 100 and 1,000 which are multiples of 10, and we have:

1,000 - 100=900, between 100 and 1,000 which are NOT multiples of 10.

The numbers available are 100 - 999      We can throw out 100 (multiple of ten)  which leaves 899 numbers available

there are 10 per each 100  (101- 901) that are multiples of TEN   except for 901-999 there are only 9 that are multiples of ten

899 - (8 x 10) - 1(9) = 810 numbers available

There are: 1,000 - 100 =900 numbers that are 3 digits.

900 /10 =90 numbers that are multiples of 10.

900 - 90 = 810 numbers that are NOT multiples of 10.