# In the city of N, with a population of one million people, flu pelicans are raging. Doctors know for sure that 0.01%

In the city of N, with a population of one million people, flu pelicans are raging. Doctors know for sure that 0.01% of residents are affected by the disease. A special blood test, which is taken by all the townspeople, helps to identify the infected. He identifies patients without errors. But if a healthy person donates blood, then in one case out of a hundred the analysis shows that he is sick. People who test positive immediately run to the pharmacy for the vaccine, which costs 1,000 rubles. How much will the vaccines be sold for?

By condition, it is known that those who are really sick will have a positive result – 0.01% of all residents of the city. The number of cases is calculated by multiplying the entire population by the percentage (share) of cases. Solution: 1,000,000 people * 0.0001 = 100 sick people
Healthy people will have a positive result in one case in a hundred. To find the number of healthy people, subtract the number of sick people from the entire population of the city and get the number of healthy people – a total of 990,900 people.
1,000,000 people – 100 people = 990,900 healthy residents
The analysis gives a false result in one case out of a hundred, to find it, we divide the number of healthy people by 100.
990,900 people / 100 = 9999 – the analysis will show that so many healthy people are sick.
Find the number of people who are really sick
9999 + 100 = 10099 people will go to buy the vaccine (that is, they are really sick)
So, in order to find the amount of vaccines sold, we multiply the amount of the vaccine by the number of sick residents
1000 * 10099 = 10,099,000