Question

Assume that the box contains 11 balls: 4 red, 5 blue, and 2 yellow. As in the text, you draw one ball, note its color, and if it is yellow replace it. If it is not yellow you do not replace it. You then draw a second ball and note its color.

(2) What is the probability that the second ball drawn is red?

Answer 1

There are 2 cases
case1
the first ball drawn is red
case 2
the first ball drawn is not red

Answer 2

ok

Answer 3

there are 4 red balls and 22 balls in total
the chance you are in case 1 is
4/22
change you are in case 2 is
18/22

when you are in case 1
you have a 3/21 chance of picking up a red ball the 2nd time
when you are in case 2
you have a 4/21 chance of picking up a red ball the 2nd time

Total prob of picking up a red is therefore
4/22*3/21 + 18/22*4/21

Answer 4

another way to view this problem is you are solvint these 2 cases