There are 5 balls in a bag. 1 ball is picked and is found to be red. What is the probability that all the balls are red assuming that the ball can be either red or green?

Explanation

There will be 5 cases and each case will be equally probable so lets find out the probability of getting 1 red ball in each case.

Case 1= 5 Red balls and 0 green ball.`P(red ball)=1.`

Case 2 = 4 Red balls and 1 green ball.`P(red ball)=4/5`

Case 3= 3 Red balls and 2 green ball.`P(red ball)=3/5`

Case 4= 2 Red balls and 3 green balls.`P(red ball)=2/5`

Case 5= 1 Red ball and 4 green balls.`P(red ball)=1/5`

now since each case is equally probable , probability of each case=`1/5`

We have to find the probability of Case 1 = `((1/5) xx 1)/( 1/5 xx ( 1+4/5+3/5+2/5+1/5))=1/3`.