In: Statistics and Probability
On Monday there will be four marbles, one red and three blue. So the probability of drawing a red marble on Monday = 1/4
On tuesday we will have 3 marbles, one red and two blue marbles as one blue marble is drawn on monday. So the probability the the red marble is picked on tuesday =
Probability of picking blue on monday * probability of picking red on tuesday
= (3/4)*(1/3) = 1/4
On Wednesday we will have 2 marbles, one red and one blue marbles as one blue marble is drawn on monday and one blue marble is drawn on tuesday. So the probability the the red marble is picked on Wednesday =
Probability of picking blue on monday * probability of picking blue on tuesday * Probability of picking red on Wednesday =
= (3/4)*(2/3)*(1/2)
= 1/4
On Thursday we will have 1 marble, one red and no blue marbles as one blue marble is drawn each on Monday, Tuesday and Wednesday . So the probability the the red marble is picked on Thursday =
Probability of picking blue on monday * probability of picking blue on tuesday * Probability of picking blue on Wednesday * Probability of picking red on Thursday
= (3/4)*(2/3)*(1/2)*(1/1)
= 1/4