Question

A bag contains 3 red balls and two blue balls. A ball is taken out random from the bag and then put back. A second ball has been taken out of the bag. What is the probability that: (a) both balls are red, (c)b both balls are the same color, (c) at least one of the balls is red. Answer

Answer 1

a . 9/25

b. 13/25

c. 3/5

Explanation:

Firstly, we add the number of balls to get the total number of balls = 3 + 2 = 5 balls

P(R) = number of red/total number of balls = 3/5

P(B) = number of blue/total number of balls = 2/5

Since the experiment is with replacement, whatever ball picked would be returned

a. Probability of both balls being red = P(R) * P(R) = 3/5 * 3/5 = 9/25

b. Probability of both balls being same color;

That is : probability of both balls being red or both being blue

Mathematically that would be;

P(R) * P(R) or P(B) * P(B)

whenever we have or in probability, what we do is to add ;

= (3/5 * 3/5) + (2/5 * 2/5) = 9/25 + 4/25 = 13/25

C. at least one of the balls is red

what this means is that both are red or one of the two is red.

Mathematically;

P(R) * P(R) or P(B) * P(R)

= (3/5 * 3/5) + (3/5 * 2/5)

= 9/25 + 6/25 = 15/25 = 3/5