Weekly service

In the class are 20 pupils. How many opportunities have the teacher if he wants choose two pupils randomly who will weeklies?

Result

n =  190

Solution: Leave us a comment of example and its solution (i.e. if it is still somewhat unclear...): Be the first to comment! To solve this verbal math problem are needed these knowledge from mathematics:

Would you like to compute count of combinations?

Next similar examples:

1. Examination The class is 21 students. How many ways can choose two to examination?
2. Class pairs In a class of 34 students, including 14 boys and 20 girls. How many couples (heterosexual, boy-girl) we can create? By what formula?
3. Confectionery The village markets have 5 kinds of sweets, one weighs 31 grams. How many different ways a customer can buy 1.519 kg sweets.
4. Ice cream Annie likes much ice cream. In the shop are six kinds of ice cream. In how many ways she can buy ice cream to three scoop if each have a different flavor mound and the order of scoops doesn't matter?
5. Chords How many 4-tones chords (chord = at the same time sounding different tones) is possible to play within 7 tones?
6. Division Division has 18 members: 10 girls and 6 boys, 2 leaders. How many different patrols can be created, if one patrol is 2 boys, 3 girls and 1 leader?
7. Fish tank A fish tank at a pet store has 8 zebra fish. In how many different ways can George choose 2 zebra fish to buy?
8. A student A student is to answer 8 out of 10 questions on the exam. a) find the number n of ways the student can choose 8 out of 10 questions b) find n if the student must answer the first three questions c) How many if he must answer at least 4 of the first 5 que
9. Trinity How many different triads can be selected from the group 43 students?
10. Blocks There are 9 interactive basic building blocks of an organization. How many two-blocks combinations are there?
11. PIN - codes How many five-digit PIN - code can we create using the even numbers? On the menu are 12 kinds of meal. How many ways can we choose four different meals into the daily menu? How many ways can divide 16 players into two teams of 8 member? The confectionery sold 5 kinds of ice cream. In how many ways can I buy 3 kinds if order of ice creams does not matter? We want to prove the sentence: If the natural number n is divisible by six, then n is divisible by three. From what assumption we started? Given a square ABCD and on each side 8 internal points. Determine the number of triangles with vertices at these points. Calculate: ?