High school + combinatorial number - examples

  1. A student
    test_14 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
  2. Families 2
    family_24 There are 729 families having 6 children each. The probability of a girl is 1/3 and the probability of a boy is 2/3. Find the the number of families having 2 girls and 4 boys.
  3. Word
    words What is the probability that a random word composed of chars T, H, A, M will be MATH?
  4. Chocolates
    Chocolate In the market have 4 kinds of chocolates. How many ways can we buy 19 chocolates?
  5. Sales
    tesco From statistics of sales goods, item A buy 51% of people and item B buys 59% of people. What is the probability that from 10 people buy 2 item A and 8 item B?
  6. N-gon
    ngon How many diagonals has convex 11-gon?
  7. Pairs
    dvojice From the five girls and four boys teachers have to choose one pair of boy and girl. A) How many such pairs of (M + F)? B) How many pairs where only boys (M + M)? C) How many are all possible pairs?
  8. Party
    party-informatikov At party overyone clink with everyone. Together, they clink 171 times. How many people were at the party?
  9. 2nd class combinations
    color_circle From how many elements you can create 4560 combinations of the second class?
  10. Lines
    lines_1 In how many points will intersect 14 different lines, where no two are parallel?
  11. Commitee
    committees A class consists of 6 males and 7 females. How many committees of 7 are possible if the committee must consist of 2 males and 5 females?
  12. Family
    stork_bocian What is the probability that a family with 7 childrens have: exactly 5 girls? 7 girls and 0 boys? Consider the birth probability of a girl is 48.69% and boy 51.31%.
  13. Bulbs
    bulb The probability that the bulb can operate 5000 hours is 0.16. What is the probability that exactly one of three bulbs can operate 5000 hours?
  14. Examination
    examination The class is 21 students. How many ways can choose two to examination?
  15. Math logic
    children_7 There are 20 children in the group, each two children have a different name. Alena and John are among them. How many ways can we choose 8 children to be among the selected A) was John B) was John and Alena C) at least one was Alena, John D) maximum one w
  16. Tournament
    turnaj Determine how many ways can be chosen two representatives from 34 students to school tournament.
  17. Cinema
    stale_kvoka How many ways can be divided 11 free tickets to the premiere of "Jáchyme throw it in the machine" between 6 pensioners?
  18. The camp
    diary At the end of the camp a 8 friends exchanged addresses. Any friend gave remaining 7 friends his card. How many addresses they exchanged?
  19. Circles
    circles How many different circles is determined by 9 points at the plane, if 6 of them lie in a straight line?
  20. Three-digit numbers
    poker_hand_ranking How many three-digit numbers are from the numbers 0 2 4 6 8 (with/without repetition)?

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