Question 740753
Say our students' names are A, B, C..., J.
_  _ _
1 2 3

Student 1 can be any of the 10 students, so we'll put a 10 there.

10
-- -- --
 1   2  3

Student 2 CANNOT be any of the 10 students, as there has already been another student chosen. Thus, the number of students is 9.

10  9
-- -- --
 1   2  3

Now that 2 students have been chosen, 8 students can be Student 3.

10  9  8
-- -- --
 1   2  3

{{{10*9*8}}}=
{{{90*8}}}=
720
Therefore, there are 720 ways for 3 out of 10 students to be chosen.