What is the minimum number of countries each of which comes

What is the minimum number of countries, each of which comes from one the 7 continents, which must be registered at the 2016 olympics game to guarantee that there are at least 40 countries that come from the same continent?

Use the pigonhole principle

please give explanation of answer

Solution

39*7 countries means there could be 39 each from each continent and still we don\'t ahve 40 from any continent

So we register: 39*7+1 so at least one continent will ahve 40 countries