Question

A box contains five red balls, six green ones, and nine yellow balls. Suppose you select one ball at random from the box and do not replace it. Then you randomly select a second ball. Find the probability that both balls will be red?

Answer 1

Answer:1/19

Step-by-step explanation:

Number of red balls: 5

Number of green balls: 6

Number of yellow balls: 9

Total number of balls= 5+6+9= 20

Let probability of red balls = Pr(red balls)

PR(red balls)= 5/20

Hence probability of picking first ball as red = 5/20

Probability of picking second ball without replacing the first ball:

This implies that by picking second ball to be red, the number of red ball would decrease by 1. Also the total number of balls would also decrease by 1 because it isn't replaced.

PR(2nd ball) = 4/19

Pr(1st ball red and 2nd ball red)= 5/20 * 4/19

=(5*4)/(20×19)

20/(20/19)

= 1/19