Postman Deliveries to Houses Without Digit 9 - How Many Houses are Delivered To?

[synkk]

Apostman delivers to in a street of houses numbered
from 1 to 1000, given that he refuses to deliver to houses with the digit 9 in the number, how many houses does he deliver to?

My working: From 0-100 he doesn't deliver to 10 houses, from 100-200 he doesn't deliver to 19 houses, 200-300 he doesn't deliver to 19 houses, 300-400 he doesn't deliver to 19 houses, from 400-500 he doesn't deliver to 19 house, from 500-600 he doesn't deliver to 19 houses, from 600-700 he doesn't deliver to 19 houses, from 700-800 he doesn't deliver to 19 houses, from 800-899 he doesn't deliver to 19 houses, from 900-100 he doesn't deliver to 99 houses.

adding them up you get 261 so 1000 - 261 you get 739. Is this correct? My friend told me it is 9^3 i.e 729, but i have no idea how he done that, could anyone explain?

 

[SammyS]

Apostman delivers to in a street of houses numbered
from 1 to 1000, given that he refuses to deliver to houses with the digit 9 in the number, how many houses does he deliver to?

My working: From 0-100 he doesn't deliver to 10 houses, from 100-200 he doesn't deliver to 19 houses, 200-300 he doesn't deliver to 19 houses, 300-400 he doesn't deliver to 19 houses, from 400-500 he doesn't deliver to 19 house, from 500-600 he doesn't deliver to 19 houses, from 600-700 he doesn't deliver to 19 houses, from 700-800 he doesn't deliver to 19 houses, from 800-899 he doesn't deliver to 19 houses, from 900-100 he doesn't deliver to 99 houses.

adding them up you get 261 so 1000 - 261 you get 739. Is this correct? My friend told me it is 9^3 i.e 729, but i have no idea how he done that, could anyone explain?

Why 729?

How many three digit numbers are there using only the nine digits, 0 through 8 ?

 

[skiller]

My working: From 0-100 he doesn't deliver to 10 houses,

Are you sure?

from 100-200 he doesn't deliver to 19 houses, 200-300 he doesn't deliver to 19 houses, 300-400 he doesn't deliver to 19 houses, from 400-500 he doesn't deliver to 19 house, from 500-600 he doesn't deliver to 19 houses, from 600-700 he doesn't deliver to 19 houses, from 700-800 he doesn't deliver to 19 houses, from 800-899 he doesn't deliver to 19 houses,

Correct.

from 900-100 he doesn't deliver to 99 houses.

Are you sure? (Even allowing for the fact that you made a typo with writing "900-100" instead of "900-1000".)