probability Q-1

speed · Posted: Mon Aug 27, 2007 8:54 pm Post subject: probability Q-1

help me to solve these probability questions

1.In a bag of balloons, the ratio of red balloons to other colours is 1:5, if 3 balloons are selected from the bag at random, what is the probability that (a) at least one balloon is red, (b) exactly one balloon is red.?

speed

ratindasgupta · Posted: Mon Aug 27, 2007 10:53 pm Post subject:

Assume that 1 balloon is red and there are 5 balloons of other colours.

Atleast 1 red = 1 - (no red)

No red = 5/6 x 4/5 x 3/4 = 1/2

Atleast 1 red = 1- 1/2 = 1/2

Exactly 1 red = (1C1 x 5C2)/6C3 = 1/2

Whats the OA?