unit: normal distribution

1. A species of alien has a mean height of 23 cm and a standard deviation of 3.6 cm. What is the probability that an alien chosen at random has a height of more than 20cm?
2. Researchers have observed that regular smokers have an average lifespan that is normally distributed and is 68 years with a standard deviation of 10 years. What percent of smokers will live beyond age 76?
3. The lifespan of a particular species of turtle is normally distributed with a mean of 180 years and a standard deviation of 40 years. What is the probability that one of these turtles will live more than a century?
4. A second species of alien has a mean height of 71 cm and a standard deviation of 5.3 cm. An alientologist discovers that 30% of them bump their heads getting into their spaceship. What is the height of the spaceship door?
5. In Bayfield, 65% of residents read the Bayfield Breeze, a local online blog. Dennis wants to know what people think of the blog, so he stops 40 people on the street to ask them if they read it.
6. Verify that the normal distribution can be used to approximate this situation.
7. What is the mean and standard deviation of the number of people he finds that read the Breeze?
8. What is the probability that at least 25 of the people he asks read the blog?
9. Yuen Zhi is running a ring toss event at a school fair. There is a 15% chance that each attempt wins a prize. She has 45 prizes and believes 250 people attempt the event. She is worried she won't have enough prizes. Can you reassure her she will probably be ok?