How many ways can a group of 3 students be chosen from a class of 30 students?

3 students can be chosen from a class of 30 in (30 x 29 x 28) = 24,360 ways.

But each group of the same 3 students will be chosen in six different ways.

The number of different groups of 3 is 24,360/6 = 4,060 .