7.3.6. An exam consists of 6 "true or false" questions. What is the 
probability a person can get five or more correct just by guessing?

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7.3.8. Ten percent of all undergraduates at a university are chemistry
majors. In a random sample of eight students, find the probability that
exactly two are chemistry majors.



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7.3.9. Thirty percent of all cars crossing a toll bridge have a commuter
sticker. What is the probability that among 10 randomly selected cars
waiting to cross the bridge at least 2 have commuter stickers?



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7.3.13 Nine customers at a supermarket are asked independently if they
use brand X laundry soap. In general, 20% of the population use this brand.
What is the probability that among the 9, more than 2 people use brand X?


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7.3.20 Every offspring inherits a gene for hair color from each parent. We
denote the dominant gene by A and the recessive gene by a. If a person has
AA or Aa then the person exhibits the dominant characteristic. We call
a person with the genes Aa a hybrid. A person with aa exhibits the recessive
characteristic. Two hybrid parents have 3 children. Find the probability
that at least one child exhibits the recessive characteristic.