# Combinatorics - math word problems

1. 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?
2. Combi-triangle On each side of the square is marked 10 different points outside the vertices of the square. How many triangles can be constructed from this set of points, where each vertex of the triangle lie on the other side of the square?
3. Green - Red We have 5 bags. Each consist one green and 2 red balls. From each we pull just one ball. What is the probability that we doesn't pull any green ball? Determine the number of integers from 1 to 106 with ending four digits 2006.
5. Combinatorics The city has 7 fountains. Works only 6. How many options are there that can squirt ?
6. Numbers How many different 3 digit natural numbers in which no digit is repeated, can be composed from digits 0,1,2?
7. Seating rules In a class are 24 seats but in 7.B class are only 18 students. How many ways can student seat? (The class has 12 benches. A bench is for a pair of students.) Result (large number) logarithm and thus write down as powers of 10.
8. Circles How many different circles is determined by 9 points at the plane, if 6 of them lie in a straight line?
9. Trinity How many different triads can be selected from the group 43 students?
10. Medals In how many ways can be divided gold, silver and bronze medal among 21 contestant?
11. Weekly service In the class are 20 pupils. How many opportunities have the teacher if he wants choose two pupils randomly who will weeklies?
12. Stacks Annie has a total of \$ 702. The money must be divided into stacks so that each buyer has the same amounth of dollars. How many options she have?
13. Cards How many ways can give away 32 playing cards to 5 player?
14. Ace From complete sets of playing cards (32 cards), we pulled out one card. What is the probability of pulling the ace?
15. Dices We will throw two dice. What is the probability that the ratio between numbers on first and second dice will be 1:2?
16. MATES In MATES (Small Television tipping) from 35 randomly numbers drawn 5 winning numbers. How many possible combinations there is?
17. Cinema How many ways can be divided 11 free tickets to the premiere of "Jáchyme throw it in the machine" between 6 pensioners?
18. Peak Uphill leads 2 paths and 1 lift. a) How many options back and forth are there? b) How many options to get there and back by not same path are there? c) How many options back and forth are there that we go at least once a lift?
19. Committees How many different committees of 2 people can be formed from a class of 21 students?
20. Cars plates How many different licence plates can country have, given that they use 3 letters followed by 3 digits?

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