### Answer to black or blue

The answer is 2/3.

To think simple, let us list out the equally likely scenarios.

1. First ball was tennis. Second ball was tennis. Rafael pulled first ball

2. First ball was tennis. Second ball was tennis. Rafael pulled second ball

3. First ball was cricket. Second ball was tennis. Rafael pulled second ball

Out of the three cases, two correspond to the first ball being tennis. Hence the answer is 2/3

Note: If we had not known that Rafael had pulled out Tennis ball, then there would be one more scenario - First ball was tennis. Second ball was tennis. Rafael pulled first ball. In that case the answer would have been 3/4

People go wrong when you take the conditional probability approach and fall into the 3/4 trap. You analyse the problem as "With two equally likely scenarios, what is the probability of getting a tennis ball". The answer for that question in 3/4. In this question, the difference is that the event has already happened and the question is the probability of the another ball also being a tennis ball.

Think deep and understand the difference I have stated above very carefully so that you dont get hunted by CAT.

And btw, the question name shud have been "yellow or red" :p

Click here for the question

To think simple, let us list out the equally likely scenarios.

1. First ball was tennis. Second ball was tennis. Rafael pulled first ball

2. First ball was tennis. Second ball was tennis. Rafael pulled second ball

3. First ball was cricket. Second ball was tennis. Rafael pulled second ball

Out of the three cases, two correspond to the first ball being tennis. Hence the answer is 2/3

Note: If we had not known that Rafael had pulled out Tennis ball, then there would be one more scenario - First ball was tennis. Second ball was tennis. Rafael pulled first ball. In that case the answer would have been 3/4

People go wrong when you take the conditional probability approach and fall into the 3/4 trap. You analyse the problem as "With two equally likely scenarios, what is the probability of getting a tennis ball". The answer for that question in 3/4. In this question, the difference is that the event has already happened and the question is the probability of the another ball also being a tennis ball.

Think deep and understand the difference I have stated above very carefully so that you dont get hunted by CAT.

And btw, the question name shud have been "yellow or red" :p

Click here for the question

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