Question

(1 point) A bowl contains 6 red balls and 6 blue balls. A woman selects balls at random without looking at them (a) How many balls must she select (minimum) to be sure of having at least three blue balls? (b) How many balls must she select (minimum) to be sure of having at least three balls of the same color?

Answer 1

1) she must have to select atleast 5 balls for getting three blue balls. Because

a) if she selects 1 ball there may be possibility of (0,1) or (1,0)

(Blue,red)

b) if she selects 2 balls there may be chance of (2,0),(0,2) or (1,1)

c) if she selects 3 balls there may be chance of (3,0),(0,3),(2,1),(1,2)

d) if she selects 4 balls there may be chance of (4,0),(0,4),(3,1),(1,3) or (2,2)

e) if she selects 5 balls there may be chance of (5,0),(0,5),(4,1),(1,4),(3,2),(2,3).

f) in worst scenario she must need to select 13 balls then there will be (3,10).

Therefore atleast 5 balls she should select for getting 3 blue balls.

2) for having three balls of same colour she have to select atkeast 6 balls(minimum)...(3,3) ie (blue,red)