Algebra
posted by Ash on .
Digit d is randomly selected from the set {1, 2, 3, 4, 5, 6, 7, 8,
9}. Without replacement of d, another digit, e is selected. What
is the probability that the two digit number de is a multiple of 3

There are 9*8 = 72 possible two digit numbers that can be formed. Those divisible by three are 12, 15, 18, 21, 24, 27, 36, 39, 42, 45, 48, 51, 54, 57, 63, 69, 72, 75, 78, 81, 84, 87, 93, and 96. That's 24 numbers.
The answer is 24/72 = 1/3