Number of integers between 1 and 1000(inclusive) with sum of digits=9
sol :x1 + x2 + x3 =9
V(n,k) = C(n-1+k , k)
this includes repeated values too (i.e) x1 and x2 and x3 can take same values
a)if the question is asked that each values should be distinct and sum up to 9 then how to solve?
b)V(n,k) = C(n-1+k , k).... does this work only for sum ?? what if question was multiplication of the digits give some value..say 290 for example
c)
