Find the probability that, given 4 red marbles and 3 blue marbles, you will get the same color from 2 times of drawing from the bag.

Question

Find the probability that, given 4 red marbles and 3 blue marbles, you will get the same color from 2 times of drawing from the bag. Hint: Make a tree diagram

Answer 1

Break down the probability into something you can solve. The probability that you will get the same color 2 times will happen if you draw 2 red or 2 blue. So calculate those probabilities. Note to find the probability that multiple events happen together--for ANDS you multiply, for ORS you add.

 

P(red and red) = 4/7 * 3/6 = 2/7

P(blue and blue)=3/7 * 2/6 = 1/7

 

To find the probability of either event happening you have to add them.

 

P(2 red or 2 blue) = P(2 red) + P(2 blue) = 2/7 + 1/7 = 3/7