Carcass wrote:
If x is to be chosen at random from the set {1,2,3}, y is to be chosen at random from the set {4,5,6}, and z is to be chosen at random from the set {7,8,9,10}, what is the probability that xyz will be even?
A. 1/9
B. 1/2
C. 2/3
D. 7/9
E. 8/9
Kudos for the right answer and explanation
One approach is to recognize that P(xyz is even) = 1 - P(xyz is NOT even)
In other words, P(xyz is even) = 1 -
P(xyz is ODD)Aside: This is a useful approach since there's only one way that xyz can be odd. x, y and z must ALL be odd for their product to be odd.
Conversely, there are
many different ways for xyz to be even.
P(xyz is odd) = P(x is odd
AND y is odd
AND z is odd)
= P(x is odd)
x P(y is odd)
x P(z is odd)
= 2/3
x 1/3
x 2/4
=
1/9So, P(xy is even) = 1 -
1/9= 8/9
Answer: E
Cheers,
Brent