Question

A bag contains 7 red, 12 white and 4 green balls. Three balls are drawn randomly. What probability that (a) 3 balls are all white (b) 3 balls are one of each color (c) 3 balls are same color​

Answer 1

1. 12 white balls
2. 23
3. 23

Explanation:

(a) Probability that 3 balls are all white:

Total number of balls = 7 red + 12 white + 4 green = 23

Number of favorable outcomes = 12 white balls

Probability = Number of favorable outcomes / Total number of possible outcomes

Probability = 12 / 23

(b) Probability that 3 balls are one of each color:

Total number of balls = 7 red + 12 white + 4 green = 23

Number of favorable outcomes = 7 red balls * 12 white balls * 4 green balls

Probability = Number of favorable outcomes / Total number of possible outcomes

Probability = (7 * 12 * 4) / (23 * 22 * 21)

(c) Probability that 3 balls are the same color:

Total number of balls = 7 red + 12 white + 4 green = 23

Number of favorable outcomes = (7 red balls * 6 red balls * 5 red balls) + (12 white balls * 11 white balls * 10 white balls) + (4 green balls * 3 green balls * 2 green balls)

Answer 2

(a) Probability that 3 balls are all white:

Step 1:

Total balls = Number of red balls + Number of white balls + Number of green balls = 7 + 12 + 4 = 23.

Step 2:

Total ways to choose 3 balls = C(23, 3) = 23! / (3 * (23-3) ) = 23 / (3 * 20) = (23 * 22 * 21) / (3 * 2 * 1) = 1771.

Step 3: Calculate the number of ways to choose 3 white balls out of 12:

Number of ways to choose 3 white balls = C(12, 3) = 12 / (3 * (12-3) ) = 12 / (3 * 9) = (12 * 11 * 10) / (3 * 2 * 1) = 220.

Step 4: Calculate the probability of selecting 3 white balls:

Probability = Number of ways to choose 3 white balls / Total ways to choose 3 balls = 220 / 1771 ≈ 0.1241.

Therefore, the probability that 3 balls drawn are all white is approximately 0.1241.

(b) Probability that 3 balls are one of each color:

Step 1: Calculate the total number of balls in the bag (same as above): Total balls = 23.

Step 2: Calculate the total number of ways to choose 3 balls out of 23 (same as above): Total ways to choose 3 balls = 1771.

Step 3: Calculate the number of ways to choose 1 ball of each color:

Number of ways to choose 1 red, 1 white, and 1 green ball = Number of red balls * Number of white balls * Number of green balls = 7 * 12 * 4 = 336.

Step 4: Calculate the probability of selecting 3 balls of different colors:

Probability = Number of ways to choose 1 ball of each color / Total ways to choose 3 balls = 336 / 1771 ≈ 0.1899.

Therefore, the probability that 3 balls drawn are one of each color is approximately 0.1899.

(c) Probability that 3 balls are of the same color:

Step 1: Calculate the total number of balls in the bag (same as above): Total balls = 23.

Step 2: Calculate the total number of ways to choose 3 balls out of 23 (same as above): Total ways to choose 3 balls = 1771.

Step 3: Calculate the number of ways to choose 3 balls of the same color:

Number of ways to choose 3 red balls = C(7, 3) = 7 / (3 * (7-3) ) = 7 / (3 * 4 ) = (7 * 6 * 5) / (3 * 2 * 1) = 35.

Number of ways to choose 3 white balls = C(12, 3) = 220.

Number of ways to choose 3 green balls = C(4, 3) = 4.

Step 4: Calculate the probability of selecting 3 balls of the same color:

Probability = (Number of ways to choose 3 red balls + Number of ways to choose 3 white balls + Number of ways to choose 3 green balls) / Total ways to choose 3 balls = (35 + 220 + 4) / 1771 ≈ 0.1416.

Therefore, the probability that 3 balls drawn are of the same color is approximately 0.1416.