Posted by Kay on Monday, November 12, 2012 at 9:56pm.
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, Monday, November 12, 2012 at 10:34pm
please?

Math  Reiny, Monday, November 12, 2012 at 11:46pm
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, Tuesday, November 13, 2012 at 12:11am
one digit is repeated twice
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