Answer:
Explanation:
There are 20 ballots, 8 have drawn a car the rest are white.
Find the probability to extract at least one ballot with the drawing of a car if not replaced:
1. If a ballot is taken out:
8 have drawn a car: thus we have 8/20 = 2/5
2. If two ballots are removed, probability of extracting 1 ballot with drawing of car is 8/20 leaving 7 out of 19 remaining. The 7/19 is the probability of drawing out a second ballot with the drawing of a car. Thus we have
8/20 * 7/19 = 56/380 = 14/95
3. If three ballots are removed, probability of extracting 1 ballot with drawing of car is 8/20 leaving 7 out of 19 remaining. The 7/19 is the probability of drawing out a second ballot with the drawing of a car leaving 6 out of 18 remaining. The 6/18 is the probability of drawing out a third ballot with the drawing of a car.
8/20 * 7/19 * 6/18 = 42/855