Hands-on math!

Washington State Math Olympiad
Hints and Solutions
2006 Grade 8 Probability and Statistics
Problem
1) In a video game, each fireball launched has a 75% chance of hitting a target. What is the probability that exactly 2 fireballs will hit the target when 2 fireballs are launched? Express your answer as a reduced fraction or as a decimal to the nearest hundredth.

2) A group of 36 students are interviewed about some items they would not want to do without. These were the results rounded to the nearest whole number percent.

What is the smallest number of students that could have selected toilet paper and zippers as items they don't want to do without?

Problem
3) A large university enrolls a student population of 85,000 students each year. The ethnic make up of the university population for last year is shown on the pie chart. This year the Asian student population percentage increased by 4% and the Hispanic population percentage by 2%. The white population percentage decreased by 9%. The other three ethnic groups each changed by the same percentage. How many Native American students are there this year?
4) The eighth grade at Sonora MS is raising money for the local food bank. Part of their fundraising is selling raffle tickets for a set of 4 tickets to a U2 concert that someone donated. Ryan really wants those tickets. He knows they go for over $50 a ticket. He's bought 10 raffle tickets so far. They're about to stop selling tickets and he finds out that about 150 raffle tickets have been sold. He wants to increase the chance that he will win to 20%. How many more tickets should he buy if no one else buys more tickets?

5) Three people meet at a party and discover they have birthdays in May. What's the chance that exactly two of their birthdays are all on the same day? May has 31 days. You may leave your answer as an expression or give your answer to the nearest hundredth.