If A can draw out the question twice, the probability that A will win the first prize just once is P2 = p1x (1-p1) x2 = 9/50.
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2) There are two ways to win the 20 yuan Prize: 15+5 10+ 10.
The probability P3 is15+5 = p1x350/500x2 =14/100.
The probability of 10+ 10 is P4 =100/500x100/500 =1/25.
So the probability of obtaining 20 yuan P (x = 20) =1/25+14/100 = 9/50.
3) The probability of winning the 30 yuan Prize P (x = 30) =110x1/kloc-0 =1/00.
The probability of winning the 25 yuan Prize P (x = 25) =110x1/5x2 = 2/50.
Probability of winning 15 yuan prize p (x =15) =1/5x7/10x2 =14/50.
The probability of winning 10 yuan prize p (x =10) = 7/10x7/10 = 49/100.