Q. A box contains 4 red, 3 green, and 2 blue marbles. If a marble is drawn and it is green, what is the probability that the next marble drawn is red?
A.0.4
B.0.5
C.0.6
D.0.3
Solution
After drawing a green marble, there are 4 red, 2 green, and 2 blue marbles left. The probability of drawing a red marble next is 4/(4+2+2) = 4/8 = 0.5.
Q. A box contains 4 white and 6 black balls. If one ball is drawn at random, what is the probability that it is black given that it is not white?
A.2/5
B.3/5
C.4/5
D.1/5
Solution
The total number of balls is 10. The number of favorable outcomes (black balls) is 6. The probability that the ball is black given that it is not white is P(Black | Not White) = 6/6 = 1.
Q. A box contains 5 red, 3 blue, and 2 green balls. If one ball is drawn at random, what is the probability that it is blue given that it is not red?
A.1/2
B.1/4
C.1/3
D.1/5
Solution
The total number of balls that are not red is 5 (3 blue + 2 green). The probability that the ball is blue given it is not red is P(Blue | Not Red) = 3/5.
Q. A box contains 5 red, 3 green, and 2 blue marbles. If a marble is drawn and it is known to be red, what is the probability that it is the first marble drawn?
A.1/5
B.1/3
C.1/2
D.1/10
Solution
The probability of drawing a red marble is independent of the order. Therefore, P(First | Red) = 1/5.
Q. A box contains 5 red, 3 green, and 2 blue marbles. If a marble is drawn at random, what is the probability that it is green given that it is not red?
A.1/2
B.1/3
C.1/4
D.1/5
Solution
The total number of non-red marbles is 5 (3 green + 2 blue). Therefore, P(Green | Not Red) = 3/5.
Q. A box contains 5 red, 3 green, and 2 blue marbles. If one marble is drawn at random, what is the probability that it is green given that it is not red?
A.1/2
B.1/3
C.1/4
D.1/5
Solution
The total number of non-red marbles is 5 (3 green + 2 blue). The probability that the marble is green given that it is not red is P(Green | Not Red) = 3/5.
