Combinatorics - problems

Would you like to compute count of combinations?

  1. Test
    test_4 The teacher prepared a test with ten questions. The student has the option to choose one correct answer from the four (A, B, C, D). The student did not get a written exam at all. What is the probability that: a) He answers half correctly. b) He answers.
  2. Desks
    desks A class has 20 students. The classroom consists of 20 desks, with 4 desks in each of 5 different rows. Amy, Bob, Chloe, and David are all friends, and would like to sit in the same row. How many possible seating arrangements are there such that Amy, Bob, C
  3. Red balls
    gule_3 In the bag there are 3 red, 12 blue and 8 green balls. How many red balls we must be attached to the bag if we want the probability of pulling out the red balls was 20%?
  4. No. of divisors
    triangle_div How many different divisors has number ??
  5. Rectangle
    diagonal In rectangle with sides 10 and 9 mark the diagonal. What is the probability that a randomly selected point within the rectangle is closer to the diagonal than to any side of the rectangle?
  6. 7 heroes
    7statocnych 5 heroes galloping on 5 horses behind. How many ways can sort them behind?
  7. Ace
    ace From complete sets of playing cards (32 cards) we pulled out one card. What is the probability of pulling the ace?
  8. Flags
    vlajka_cz How many different flags can be made from colors white, yellow, red, blue, green, orange so that each flag consisted of three different colors?
  9. Vans
    shuttlevan In how many ways can 8 shuttle vans line up at the airport?
  10. Seating
    kupe_1 How many ways can 7 people sit on 3 numbered chairs (eg seat reservation on the train)?
  11. Pediatrician
    doctor Pediatrician this month of 21 working days takes 3 days holidays. What is the probability that on Monday will be at work?
  12. Bureau of Labor
    UPSVAR Bureau of Labor is a state institution that provides mike and the rest for their so-called clients. The mission of the Bureau of Labor is spend taxpayer money to provide relaxation and benefits to those who do not want to work. Popularly speaking sense the
  13. Guests
    hostia How many ways can 7 guests sit down on 9 seats standing in a row?
  14. 2nd class variations
    cards From how many elements you can create 6480 variations of the second class?
  15. Word
    words What is the probability that a random word composed of chars M, R, P, E, I, O, G, S, S, G, R, T, E, C, E, N, I, O, O, R will be GEOMETRICPROGRESSION?
  16. Shelf
    bookshelf.JPG How many ways are there to arrange 9 books on a shelf?
  17. Phone numbers
    old_phone How many 9-digit telephone numbers can be compiled from the digits 0,1,2,..,8,9 that no digit is repeated?
  18. Chocolates
    Chocolate In the market have 3 kinds of chocolates. How many ways can we buy 13 chocolates?
  19. Rectangles
    rectangles How many rectangles with area 2832 cm2 whose sides is natural numbers are?
  20. Two doctors
    dr_cvach Doctor A will determine the correct diagnosis with a probability 80% and doctor B with a probability 72%. Calculate probability of correct diagnosis if patient is diagnosed by both doctors.

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