Paul is working at a university. He is part of a big project, which involves 70 scientists in total. Half of them are from Europe and one-fifth are from Canada. The rest are from the USA. How many scientists in this project are from the USA? Let's be accurate as possible.
Of all the scientists taking part in the project, half of them are from Europe, which means 70 * 0.5 = 35 people. The number of researchers from Canada is 70 * 1 / 5 = 14 people. That means there are 70 - 35 - 14 = 21 researchers from the USA.
The answer: 21.