# Combinatorics - math word problems

1. Digits How many odd four-digit numbers can we create from digits: 0, 3,5,6,7? On the menu are 12 kinds of meal. How many ways can we choose four different meals into the daily menu?
3. Bookshelf and books How many ways can we place 7 books in a bookshelf?
4. Probability of intersection Three students have a probability of 0.7,0.5 and 0.4 to graduated from university respectively. What is the probability that at least one of them will be graduated?
5. A jackpot How many times must I play this jackpot to win? A jackpot of seven games having (1 X 2), i. E. , home win or away win.
6. Three-digit integers How many three-digit natural numbers exist that do not contain zero and are divisible by five?
7. Classroom Of the 26 pupils in the classroom, 12 boys and 14 girls, four representatives are picked to the odds of being: a) all the girls b) three girls and one boy c) there will be at least two boys
8. STRESSED word Each letter in STRESSED is printed on identical cards, one letter per card and assembled in random order. Calculate the probability that the cards spell DESSERTS when assembled.
9. Three workplaces How many ways can we divide nine workers into three workplaces if they need four workers in the first workplace, 3 in the second workplace and 2 in the third?
10. A pizza A pizza place offers 14 different toppings. How many different three topping pizzas can you order?
11. Family 94 boys are born per 100 girls. Determine the probability that there are two boys in a randomly selected family with three children.
12. Boys and girls There are 11 boys and 18 girls in the classroom. Three pupils will answer. What is the probability that two boys will be among them?
13. Three numbers We have three different non-zero digits. We will create all 3 digits numbers from them to use all 3 figures in each number. We add all the created numbers, and we get the sum of 1554. What were the numbers?
14. Pages counting There are pages numbered from 2 to 104 in the book. How many digits have to be printed to number the pages?
15. Three shooters Three shooters shoot, each one time, on the same target. The first hit the target with a probability of 0.7; second with a probability of 0.8 and a third with a probability of 0.9. What is the probability to hit the target: a) just once b) at least once
16. Internet anywhere In school, 60% of pupils have access to the internet at home. A group of 8 students is chosen at random. Find the probability that a) exactly 5 have access to the internet. b) At least 6 students have access to the internet
17. Practice How many ways can you place 20 pupils in a row when starting on practice?
18. Each with each Five pupils from 3A class played table tennis. How many matches did they play with each other?
19. Election 4 In a certain election there are 3 candidates for president 5 for secretory and 2 for tresurer. Find how many ways the election may (turn out/held).
20. Perfect cubes Suppose a number is chosen at random from the set (0,1,2,3,. .. ,202). What is the probability that the number is a perfect cube?

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