Probability change

Suppose i have a set [A,B,C]
Probability of A =10% B=40% C=50%
If probability of C lowers to 25%, how the remainder value is distributed(proportionaly)?
I know it suppose to get like 15(+50%),60(+50%),25 but what if the set grows?
exmaple       5,77,3,15(-5) becomes 6.65,102,4,10
I'm looking for a formula for arbitrary sets of probability(not just 3).

>>9
letter1 'A' with letter2 'B' give 0.1% probability that letter3 will be 'Z'
computer generates random letters using 0%[prob1][prob2][prob3]100% intervals
letter3 will be in the one interval on which the probability lands.
By shrinking the interval(and proportionally adjusting all others) the probability is reduced(as set by tester or file input).  
the current 2 letter generate third, then second and third generate fourth,etc. at random word length(2-16) the word is printed to screen.