A professor must randomly select 4 students to participate in a mock debate. There are 20 students in his class. In how many different ways can these students be selected, if the order of selection does not matter?
A. 3,945
B. 4,845
C. 2,880
D. 116,280

Question

A professor must randomly select 4 students to participate in a mock debate. There are 20 students in his class. In how many different ways can these students be selected, if the order of selection does not matter?
  		A. 	3,945
  		B. 	4,845
  		C. 	2,880
  		D. 	116,280

solomonzelman · Answer

This time it sounds like it is combinations rather than permutations.

$\normalsize\color{blue}{  20~C~4  }$

solomonzelman · Answer

$\large\color{blue}{  20~C~4~=~\frac{20!}{4!(20-4)!}  }$

solomonzelman · Answer

can you finish the prob?

anonymous · Answer

i forgot what ! means by a number haha

solomonzelman · Answer

$\normalsize\color{blue}{   5!= 1 \times 2\times 3 \times 4 \times 5  }$   OR
$\normalsize\color{blue}{   n!= 1 \times 2\times 3 \times 4 \times...\times ~(n-2) \times ~(n-1)~ \times n. }$   and/or

See ?

anonymous · Answer

yes i sees

anonymous · Answer

can i just have the answer cuz i don't wanna do the solving stuff

anonymous · Answer

400/400*256 @SolomonZelman

solomonzelman · Answer

you will have to do solving at some point, do it before it's too late.