Question 1086262: how many no. lying between 10 and 1000 can be formed from the digits 1,2,3,4,5,6,7,8,9
Answer by josmiceli(19441)   (Show Source):
You can put this solution on YOUR website! They don't say if the numbers include
10 and 1000, but I'll assume they do.
1 through 9 is 9 numbers, and 0 is excluded
----------------------------------------
10, 20, 30, . . . 90 will be excluded ( 9 numbers )
------------------------------------------
10x and
1x0
are excluded where x = 0 - 9 ( 20 numbers )
------------------------------------------
20x and
2x0
are excluded ( 20 numbers )
----------------------------
Keep going, and this is 20 x 9 = 180 numbers
----------------------------
180 + 9 = 189 are excluded
------------------------------
10 through 1000 inclusive = 991 numbers
------------------------------
991 - 189 = 802
802 numbers can be formed from
1 through 9
------------------------------
Note that if 10 and 1000 are not included in the count
then 800 numbers can be formed
--------------------
feel free to get another opinion on this
|
|
|
