VJesus12 wrote:A certain box contains only red balls and green balls. If one ball is randomly selected from the box, what is the probability that it is red?

(1) Red balls comprise exactly two-thirds of all the balls in the box.

(2) The probability of selecting a green ball from the box is 1/3.

The OA is the option D.

Could someone clarify this question to me? Why is the option D correct? I think the answer should be B.

Please, someone, bring some light here.

We have to find out the probability of getting a red ball upon drawing one ball randomly from the box that has only red and green balls.

Probability of getting a red ball = Number of red balls / total number of balls

Let's take each statement one by one.

(1) Red balls comprise exactly two-thirds of all the balls in the box.

Say there are 3 balls, thus, there are 2/3*3 = 2 red balls and 3 - 2 = 1 green ball.

Probability of getting a red ball = Number of red balls / total number of balls = 2/3. Sufficient.

(2) The probability of selecting a green ball from the box is 1/3.

We know that

the probability of getting a red ball + the probability of getting a green ball = 1

the probability of getting a red ball = 1 - the probability of getting a green ball

the probability of getting a red ball = 1 - 1/3 = 2/3. Sufficient.

The correct answer: D

Hope this helps!

-Jay
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