# Percentages + probability - math problems How large must the group of people be so that the probability that two people have a birthday on the same day of the year is greater than 90%?
2. All use computer It is reported that 72% of working women use computers at work. Choose 3 women at random, find the probability that all 3 women use a computer in their jobs.
3. The manufacturer The manufacturer found that 3% of the plates produced had a malfunction. Of the compliant, 75% are first and 25% second. What is the probability of producing first and second class plates?
4. Probability How probable is a randomly selected three-digit number divisible by five or seven?
5. The test The test contains four questions, and there are five different answers to each of them, of which only one is correct, the others are incorrect. What is the probability that a student who does not know the answer to any question will guess the right answer
6. Corona again If the population on long island is 7.75 million and the coronavirus has affected 22,178. What percent of the population is affected. (looking for 1 in? If possible)
7. The university At a certain university, 25% of students are in the business faculty. Of the students in the business faculty, 66% are males. However, only 52% of all students at the university are male. a. What is the probability that a student selected at random in t
8. Sick days In Canada, there are typically 261 working days per year. If there is a 4.9% chance that an employee takes a sick day. .. what is the probability an employee will use 17 OR MORE sick days in a year?
9. Auto-tuning During auto-tuning, the TV searched for 25 channels, four of which were music. The channels are stored in the TV's memory in random order. Express the percentage of the event that the music channel will be saved first.
10. Lathe 95% of the components manufactured on the lathe comply with the standard, of which 80% of the components are first-class. How likely can we expect a manufactured part to be first class?
11. STRESSED word Each letter in STRESSED is printed on identical cards, one letter per card and assembled in random order. Calculate the probability that the cards spell DESSERTS when assembled.
12. Family 94 boys are born per 100 girls. Determine the probability that there are two boys in a randomly selected family with three children.
13. Internet anywhere In school, 60% of pupils have access to the internet at home. A group of 8 students is chosen at random. Find the probability that a) exactly 5 have access to the internet. b) At least 6 students have access to the internet
14. Left handed It is known that 25% of the population is left-handed. What is the probability that there is a maximum of three left-handers at a seminar where there are 30 participants?
15. Prime number Jan wrote any number from 1 to 20. What is the probability that he wrote the prime number?
16. Component fail There is a 90 percent chance that a particular type of component will perform adequately under high temperature conditions. If the device involved has four such components, determine the probability that the device is inoperable because exactly one of the
17. Utopia Island A probability of disease A on the island of Utopia is 40%. A probability of occurrence among the men of this island, which make up 60% of all the population (the rest are women), is 50%. What is the probability of occurrence of A disease among women on Ut
18. Red balls In the bag there are 3 red, 12 blue and 8 green balls. How many red balls we must be attached to the bag if we want the probability of pulling out the red balls was 20%?
19. Sum on dice We have two dice. What is the greater likelihood of fall a total sum 7 or 8 ? (write 7, 8 or 0 if the probabilities are the same)?
20. Three reds What is the probability that when choosing 3 carats from seven carats, all 3 reds will be red?

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