Question

You have a 3-card deck containing a king, a queen, and a jack. You draw a random card, then without putting it back you draw a random second card from the ones that are left. Use a tree diagram to calculate the probability that you draw exactly 1 jack.

Answer 1

First probability: 2/3 (you can take either a K or Q)
Second probability: 1/2 (you can take either a K or Q, depending on which one is left)
2/3*1/2 = 1/3

Answer 2

@daniel I think you got it wrong. ..... What abt the case when jack can be drawn first, and in the second draw there can be a king or queen? I think the correct answer would be (1/3)*1 + (2/3)*(1/2) = (1/3)+(1/3)=2/3

Answer 3

Woops: I really messed up on this one: I read it so that you had to be left with one Jack.
You are 100% correct: 2/3