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Washington State Math Olympiad
Hints and Solutions
2011 Grade 7 Probability and Statistics
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| Problem |
1) At the local middle school math night, one game has a grand prize that everyone wants. To play and win you need to get three 6's. There are two options:
Option 1: roll a regular
number cube with the numbers 1 to 6 on it three times and hopefully roll a 6 each time.
Option 2: pull three balls from a bin that contains 18 balls; each ball has one number on it
and there are three balls for each number from 1 to 6.
Which option is better and why? Include the probabilities for both options in your answer.
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2) Lena is signing up for classes at her summer camp. She wants to take gymnastics, horseback riding, drawing, and theatre just like her friend Rhoda. Gymnastics and drawing are offered all four sessions. Horseback riding is offered session 2 and 3. Theatre is offered session 1 and 4. Campers take one class a session. She wants the same schedule Rhoda has; Gymnastics, drawing, horseback riding and theatre, in that order. If she is
assigned randomly to a schedule that includes her four choices, what is the probability she will get the same schedule as Rhoda?
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3)
Three cousins all have birthdays that fall on the 27th day of different months and none were born in a leap year. What is the probability of that happening? Express your answer as a fraction, you need not reduce it.
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