Question

The Sum of digits integers X is 2 where 10^10 < X < 10^11 find the number of arrangements of X?

Answer 1

=_= The numbers are :

-> 10000000001
-> 10000000010
-> 10000000100
-> 10000001000
-> 10000010000
-> 10000100000
-> 10001000000
-> 10010000000
-> 10100000000
-> 11000000000
-> 2000000000

Are you serious =_! You can count this on hands huh

#Anyways, fix a '1' at the mean position and you can get 10C1 way of arranging one remaining among 10 spaces

*Also, with 2 at leftmost position, you have one more no.

#Have fun with doing Combinatorics on hand (lol)

--->>>> Total 11 Arrangements <<<<------

@Yuichi