Posted by Kay on .
I form a 3digit number at random from the digits 19. What is the probability that my number has no repeated digits? All three digits the same? Exactly one repeated digit?

Math 
Kay,
please?

Math 
Reiny,
number of cases with no repeating digits
= 9x8x7 = 504
number of cases where digits repeat
= 9x9x9 = 729
so prob(no repeating digits) = 504/729 = 56/81
all 3 digits repeat, could be 111 , 222, .. 999
or 9 of them
prob = 9/729 = 1/81
I am not clear what you mean by "exactly one repeated digit" 
Math 
Kay,
one digit is repeated twice