21.A coin is tossed 3 times. the probability of getting exactly 2 heads, is

22.Two players A and B play a game in which their chances of winning are in the ratio 3:2. A chance of winning at least 2 games out of 3, is

23.A person draws a card from a pack of playing cards, replaces it and shuffles the pack. He continues doing this until he draws a spade. The chance that he fails the first two times, is

24.A six faced dice is so biased that it is twice as likely to show an even numbre as an odd number when thrown. It is thrown twice. The probability that the sum of two numbrs thrown us eveb us

25.A, B, C take one shot each at a target. Their probabilities of hitting the target are respectively 0. 4, 0.5 and 0.8. The probability that at least two of them hit the target, is