Probability of choosing a red ball out of two boxes with red and white balls?

Question

Box 1 has 2 white balls and 4 red balls, box 2 has 3 white balls and 3 red balls. There is a 75% chance of choosing box 1 and a 25% chance of choosing box 2. What is the probability of choosing a red ball?

Answer 1

If you have learned conditional probability you can use:

 

P(R) = P(Box1)P(R|Box1) + P(Box2)P(R|Box2)

 

Do you understand this formula?