Probability and Statistics

From Washington State 1996 Math Olympiad sponsored by WSMC
1). (2 points) Of all the families that have only two children, what is the probability that at least one is a girl?




Answer:__________

TEAM NO ____ TEAM MEMBERS:

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2). (3 points) A bag contains red, white and blue marbles. The probability of drawing a red marble is 1/3 and the probability of drawing a white marble is 1/5. What is the probability of drawing a blue marble?


Answer:__________


3). (3 points) A bag contains 2 yellow marbles, 4 blue marbles and 6 red marbles. How many blue marbles must be added to the bag to make the probability of drawing a blue marble 1/2 or 50%?


Answer:__________


4). (3 points) In a game you flip 3 chips. Chip #1's sides are blue and red; #2's are blue and white; and #3 has red and white. The first player gets a point if any 2 chips match. To be fair, how many points should the second player get if all 3 chips are different?


Answer:__________


5). (3 points) A bag has 10 candies. We drew a candy out, looked at it, and put it back 10 times, and we noticed we got 4 fireballs. We repeated the experiment four times and got 2, 5, 4, and 2 fireballs. How many fireballs are most likely to be in the bag?


Answer:__________