Question

A teacher grades homework by randomly selecting 4 out of 10 homework problems to grade. How many different groups of 4 problems can be taken from the assignment of 10 problems?

Answer 1

use combinations
\[nCr = \frac{n!}{r!(n-r)!}\]
so
\[10C4 = \frac{10!}{4!(10-4)!}\]
does that help?

Answer 2

so do i multiply

Answer 3

what do you mean?

Answer 4

how do i get the different groups

Answer 5

you solve what i wrote above \[\frac{10!}{4!(10-4)!}\]
you know what those notations mean right?

Answer 6

36

Answer 7

that's not right....what did you do?

Answer 8

4x10=-4

Answer 9

4x10 is not -4.... what do you mean 4x10 = -4?

Answer 10

4x10=40-4=36

Answer 11

hmm well no...that's not how to do it..

Answer 12

10! = 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

4! = 4 x 3 x 2 x 1

(10-4)! = 6! = 6 x 5 x 4 x 3 x 2 x 1

now can you solve it?

Answer 13

3628800
24
720

Answer 14

??

Answer 15

i just multiply

Answer 16

so it 4

Answer 17

?