We use cookies to ensure you have the best browsing experience on our website. Please read our cookie policy for more information about how we use cookies.
Using the pairs given, we can compute how many countries are there(say, g) and how many people are there in each of these countries.
In the above example, there are 3 countries, the 1st has 7 ppl, the 2nd has 2 ppl and the 3rd has just 1 person.
Since 2 ppl from diff. countries need to be sent, there are gC2 ways of choosing a pair of countries,in this case there are 3 countries, so 3 ways of choosing a pair of countries.
Say, in one of these combinations, if countries i and j are chosen, then the no. of ways in which you can select the ppl from these 2 countries is (#of ppl in country i)*(#of ppl in country j), and this quantity is summed up over all the gC2 combinations.
In this case, with the 3 combinations being:
choosing countries 1 and 2: 7*2
choosing countries 2 and 3: 2*1
choosing countries 1 and 3: 7*1
Journey to the Moon
You are viewing a single comment's thread. Return to all comments →
Using the pairs given, we can compute how many countries are there(say, g) and how many people are there in each of these countries. In the above example, there are 3 countries, the 1st has 7 ppl, the 2nd has 2 ppl and the 3rd has just 1 person.
Since 2 ppl from diff. countries need to be sent, there are gC2 ways of choosing a pair of countries,in this case there are 3 countries, so 3 ways of choosing a pair of countries. Say, in one of these combinations, if countries i and j are chosen, then the no. of ways in which you can select the ppl from these 2 countries is (#of ppl in country i)*(#of ppl in country j), and this quantity is summed up over all the gC2 combinations.
In this case, with the 3 combinations being: choosing countries 1 and 2: 7*2 choosing countries 2 and 3: 2*1 choosing countries 1 and 3: 7*1
Summing it up, we get 23.