Examination

The class is 21 students. How many ways can choose two to examination?

Correct result:

n =  210

Solution:

n=C2(21)=(212)=21!2!(212)!=212021=210n = C_{{ 2}}(21) = \dbinom{ 21}{ 2} = \dfrac{ 21! }{ 2!(21-2)!} = \dfrac{ 21 \cdot 20 } { 2 \cdot 1 } = 210



We would be very happy if you find an error in the example, spelling mistakes, or inaccuracies, and please send it to us. We thank you!






Showing 0 comments:
avatar




Tips to related online calculators
Would you like to compute count of combinations?

You need to know the following knowledge to solve this word math problem:

Next similar math problems:

  • 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 ques
  • Weekly service
    school_table.JPG In the class are 20 pupils. How many opportunities have the teacher if he wants choose two pupils randomly who will weeklies?
  • Trinity
    trojka How many different triads can be selected from the group 43 students?
  • Fish tank
    zebra_fish A fish tank at a pet store has 8 zebra fish. In how many different ways can George choose 2 zebra fish to buy?
  • Volleyball
    volejbal 8 girls wants to play volleyball against boys. On the field at one time can be six players per team. How many initial teams of this girls may trainer to choose?
  • Today in school
    skola There are 9 girls and 11 boys in the class today. What is the probability that Suzan will go to the board today?
  • Teams
    football_team How many ways can divide 16 players into two teams of 8 member?
  • Confectionery
    cukrovinky The village markets have 5 kinds of sweets, one weighs 31 grams. How many different ways a customer can buy 1.519 kg sweets.
  • Chords
    chords How many 4-tones chords (chord = at the same time sounding different tones) is possible to play within 7 tones?
  • Blocks
    cubes3_1 There are 9 interactive basic building blocks of an organization. How many two-blocks combinations are there?
  • PIN - codes
    pin How many five-digit PIN - code can we create using the even numbers?
  • Calculation of CN
    color_combinations Calculate: ?
  • Balls
    spheres_1 The urn is 8 white and 6 black balls. We pull 4 randomly balls. What is the probability that among them will be two white?
  • One green
    gulicky In the container are 45 white and 15 balls. We randomly select 5 balls. What is the probability that it will be a maximum one green?
  • Wheelchair
    vozik The boy pushes the wheelchair with a force of F1 = 20N. The wheelchair exerts a force of F2 on the boy. How large is this force?
  • Sequence
    seq_1 Write the first 6 members of these sequence: a1 = 5 a2 = 7 an+2 = an+1 +2 an
  • Reference angle
    anglemeter Find the reference angle of each angle: