Probability (again, thanks)?

Question

A number is picked at random from the digits { 1,2,3,4,5,6,7,8,9 }. Given that the number is a multiple of 3, find the probability that the number is

(a) even;

even numbers are 2,4,6,8

so,

4/9 is the answer

[but the correct answer is 1/3]

they said they want EVEN numbers. but why..

(b) a multiple of 4

my answer:

multiple of 4 = 4,8

so,

2/9 is my answer.

but the correct answer is 0..

[why..? i thought they said they want a multiple of 4, which are 4 and 8.. isn't it...]

thank youuu.

Answer 1

a) It's GIVEN that the number is a multiple of 3. That is, the number is 3, 6, or 9. Only one of the three numbers is even (6), so the probability is 1/3.

b) Again, it is GIVEN that the number is a multiple of 3. There are no multiples of 3 that are also multiples of 4, so the probability is 0.

Answer 2

(a) Well, it's GIVEN that the number is a multiple of 3, which means it can be either 3, 6, or 9. Therefore, the probability that the number is even would be 1/3.

(b) Since it's GIVEN that the number is a multiple of 3, then there would be NO multiple of 4 so far since it's only up to 9.

Hope this helps!